Thyroid Nodules Research Articles

8229 Prevalence of Thyroid Cancer in Patients with Hashimotos Thyroiditis Presenting Concomitant Thyroid Nodular Disease

Abstract Disclosure: M.A. Alvarez Castillo: None. L. Sanchez Arriaga: None. A. Segovia Palomo: None. Introduction: Hashimoto's thyroiditis (HT) is the most frequent autoimmune thyroid disease and the main cause of goiter and hypothyroidism; it induces a process of aseptic autoimmune inflammation. Fibroinflammatory changes lead to the development of thyroid nodules (TN), additionally chronic inflammation is an important player in the development of cancer, although this association is controversial. The prevalence of thyroid cancer (TC) in patients with HT ranges from 0.61-58.4% (25.01%), being higher than in patients with TN without concomitant HT. Objective: To know the prevalence of malignancy in patients with HT who present thyroid nodular disease. Methodology: An observational, descriptive, retrospective, and longitudinal study was carried out. Patients with HT diagnosis were selected by measuring Ab TPO and/or Ab TG who presented an ultrasound diagnosis of TN and FNAB of the thyroid lesion had been performed. Descriptive statistics and linear regression were used. Results: 87 patients: 6 (6.9%) men and 81 (93.1%) women aged 47.9 (12.7) years. 4 (4.5%) required FNAB in 2 TN, for a total of 91 TN studied. 64% had a diagnosis of hypothyroidism and were taking LT4, TSH 4.40 (4.44) mUI/mL, FT4 1.00 (0.27) ng/dL. Mean Ab TPO was 794.7 ± 1354.6. Diagnosis time 19.5 (29.1) months. 39.6% the detection was made by the patient and 35.2% by the doctor. Major axis was 18.8 (12.1) mm. Ultrasound pattern of single TN 58.2% and multinodular 41.8%. Median TIRADS was 4, with a mode of 5. 81.3% reported Bethesda II and 18.7% malignant or suspected, were sent for surgery, malignancy was confirmed in 16/ 17 lesions. 14 (15.3%) were TPC and 2 lymphomas, the main subtypes were classic papillary and NHL, respectively. Mode of ATA risk was intermediate. Multivariate analysis only TIRADS represented risk factor (OR 2.08) Conclusions: The frequency of TC in our population was 15.3%, which reflects a higher prevalence of malignancy in thyroid nodules in patients with chronic thyroiditis, in accordance with what has been reported in other series. Presentation: 6/3/2024

8414 Utilization of Cell Free DNA Integrity Index to Differentiate Benign from Malignant Thyroid Nodules

Abstract Disclosure: S. Tarafdar: None. S. Dutta: None. P. Mukhopadhyay: None. N.P. Bhattacharya: None. S. Ghosh: None. Introduction: Recent advances in molecular genetics have evaluated a potential role for plasma cell-free DNA (cfDNA) integrity index as a non-invasive cancer marker. Data on cfDNA integrity in differentiated thyroid cancer is sparse and needs to be investigated further. Aim of the study: The purpose of this study is to investigate the hypothesis that longer DNA strands in plasma may serve as a marker for thyroid cancer. Methods: Patients presenting with thyroid nodules underwent ultrasonography with Thyroid Image Reporting and Data Systems (TIRADS) scoring and FNAC (Bethesda classification).Patients with Bethesda 3, 4, 5, and 6 had surgery and confirmation by histopathology. Patients with Bethesda 2 presenting with compressive symptoms and cosmetic concerns underwent surgery; the remaining patients were considered benign based on clinical follow-up, USG, and FNAC characteristics. Blood sample collected prior to FNAC was used to extract and quantify cfDNA. To assess the integrity index 180/67, 306/67, and 476/67 for the APP gene, we used a quantitative real-time PCR (qPCR) method based on the quantification of four amplicons of varying lengths (67, 180, 306, and 476 bp, respectively). Because culture cells had extremely intact genomic DNA, the genomic DNA obtained from the MDA-T32 papillary thyroid cancer cell line was utilised as a reference to estimate the relative DNA strand integrity in plasma DNA. To determine the (ΔCt) value for 67,180, 306, and 476 bp, the Ct value of the sample was subtracted from that of the MDA-T32 control. Results: A total of 161 subjects were recruited, of these 92 were benign and 69 had differentiated thyroid cancer(confirmed by histopathology). Using the 180/67 bp integrity index benign thyroid nodule patients had significant lower value (median 0.39, 95% CI: 0.33-0.46) compared to patients with differentiated thyroid cancer (median 0.62, 95% CI: 0.56-0.68). A cfDNA integrity index of 180/67 bp could significantly differentiate between benign and malignant thyroid nodules (P<0.001). However, there was no significant difference between malignant and benign thyroid nodules based on the cell free DNA integrity indexes of 306/67 and 476/67. Conclusions: The cfDNA integrity score of 180/67 exhibits potential as a circulating marker for the detection of thyroid nodules and as a means of monitoring cfDNA fragmentation in patients with thyroid cancer. However, further confirmation through prospective trials is necessary. Presentation: 6/3/2024

7812 Community Practice Setting Experience in Evaluation of Incidental Thyroid Nodules

Abstract Disclosure: N. Abate: None. H. Rhodes: None. M. Horlavadi: None. B. Adams-Huet: None. M. Chandalia: Advisory Board Member; Self; Boehringer Ingelheim. Speaker; Self; Boehringer Ingelheim, Eli Lilly & Company, Novo Nordisk. Background: There is a significant increase in detection of incidental thyroid nodules due to increase in routine screening ultrasounds at church, workplace, and health fairs, increase in routine ultrasound in primary care clinics and incidental finding of thyroid nodule during carotid artery ultrasound. These patients are then referred for thyroid nodule fine needle aspiration biopsy. Aim of this study was to evaluate real world data in frequency of thyroid cancer in patients referred for incidental thyroid nodule to a nonacademic Endocrinology clinic utilizing centralized collection of cytology and molecular analysis. Method: Medical records were reviewed for consecutive FNA of incidental thyroid nodule in an Endocrinology clinic in greater Houston from 2021 to 2023. FNA was performed in patients selected based on ACR TI-RADS classification. Patients with Bethesda score of 3 or more had molecular testing with Thyroseq performed. Patients with intermediate or high probability of cancer on Thyroseq as well as Patients with Bethesda 4 and 5 on cytopathology were referred for surgery. Surgical pathology was obtained in patients who underwent surgery. Data was tabulated and analyzed using SAS. Results: A total of 304 subjects, 267 Female and 37 males, age 57 ± 13, nodule size 2.69 ± 1.4 (mean ± SD), had thyroid nodule FNA between 2021 and 2023. Of these FNA, 23 (7.5%) sample collections were insufficient, 233 (77.3%) were benign (Bethesda 2), 46 (15%) were Atypia of undetermined significance or Suspicious for malignancy. Of those subjects with Bethesda 3 or higher, 36 patients had molecular testing by Thyroseq Method. Fifteen patients had intermediate and high risk finding on Thyroseq. Thirty-four subjects had surgery and 8 patients had malignancy on surgical pathology. One patient was identified as Medullary Thyroid cancer on Thyroseq, confirmed by surgery. Frequency of malignancy in incidentally detected thyroid nodule in the whole group was 2.6%, those with Bethesda 3 and more was 17.4% and those with Thyroseq intermediate or high risk was 27%. Conclusion: Availability of centralized cytopathology and reflex molecular testing to Community practice settings helps reducing unnecessary thyroid surgeries in patients with incidental thyroid nodules. Presentation: 6/1/2024

7637 Characteristics of Thyroid Nodules Among Adolescents and Adults in Medina, Saudi Arabia

Abstract Disclosure: R. Alradadi: None. M. Sindi: None. O. Alrehaili: None. S. Alanazi: None. S. Alahmadi: None. F. Mansuri: None. A. Zain: None. Background: Thyroid Nodules are common clinical finding, with a prevalence of about 20% in young adults and around 70% in the elderly population. A significant increase in the incidence rate of Thyroid Cancer in our population has been noted, over the past 30 years. The aim of the study is to define the characteristics of Thyroid Nodules in adolescents and adults in our region compared to what published worldwide. Method: A retrospective chart review, conducted at our Health Institution. The study included adolescents and adult who had Thyroid Nodules and was seen in the outpatient endocrine clinic in the period between 2018 and 2022, using non-probability consecutive sampling. Patient medical records provided demographic, medical, and laboratory data, and the analysis employed SPSS for statistical assessment​​. Data collection conducted from October through December of 2023 Result: Out of the total sample of 552 patients, there were 84.8% females. More than half of the patients (55.9%) were between 36-55 years of age. 57.4% of patients were overweight or obese. 56.4% presented with goiter. FT3, FT4 and TSH levels were normal among 88.4%, 78% and 83.3% respectively. Anti TPO antibodies were reported in 14.2% as compared to thyroglobulin antibodies in 2.2%.Follicular neoplasm/suspected neoplasm was detected among 8.15% of the sample. Papillary thyroid carcinoma [27/41] was the most frequent finding with positive FNA. Multiple nodules were more prevalent 38.8% as compared to solitary nodules in 34.1%. The right sided nodules were mostly solid 49.2% while hypervascularity was noted in 9.1% and51.4% were of more than 1.5cm. In contrast, left lobe nodule 37% were found to be solid and 6.2% showed hypervascularity and size was more than 1.5cm in 45% of the left nodules Conclusion: The vast majority of adults and adolescents with thyroid nodule were female as expected based on what reported from previous studies. Preexisting Thyroid Diseases present in only small number of patients 15.4 %. Anti-TPO antibody was more predominant than Thyroglobulin Antibody. Follicular neoplasm/suspected neoplasm was detected among 8.15% of the sample. Papillary thyroid carcinoma was the most frequent finding among the positive FNA results. Presentation: 6/3/2024

7639 A Rare Cause of Lung Adenocarcinoma with Metastasis to the Thyroid

Abstract Disclosure: E. Echevarria-Torres: None. C.G. Yap: None. K.E. Izuora: None. A rare cause of lung adenocarcinoma with metastasis to the thyroid. Metastasis to the thyroid gland from non-thyroid malignancies is rare. When metastasis occurs, presenting symptoms are typically nonspecific, representing a diagnostic challenge. With the goal of raising awareness, we present a case of lung adenocarcinoma with metastasis to the thyroid. An 85-year-old man with a history of hypertension, hyperlipidemia and 60 years smoking history presented to the endocrine clinic for evaluation of subclinical hyperthyroidism. On the physical exam, there was fullness in the right thyroid area which on ultrasound showing a large right thyroid nodule occupying the entire lobe. There was also a solid 4.5 cm x 3.4 cm x 4.6 cm nodule in the mid-anterior left thyroid lobe. Fine needle aspiration cytology of right nodule revealed malignant cells and cell block material positive for TTF-1 (Thyroid Transcription Factor 1) concerning for malignancy. The left thyroid nodule cytology was consistent with benign follicular nodule. Chest CT ordered for surgical planning showed right upper lobe pleural-based lung opacity measuring 3.7 cm x 2.9 cm with supra clavicular lymphadenopathy. Biopsy of lung mass and supra clavicular lymph nodes revealed primary lung adenocarcinoma involving the lymph nodes consistent with stage Iva (cT3NxM1b). The patient was referred to oncology for further management. Discussion: Metastatic lesions to the thyroid gland account for less than 1 % of all malignant thyroid tumors with most cases found on autopsy. This is hypothesized to be due to the rich blood supply and high iodine content of the thyroid gland. Thyroid metastasis usually presents several years after initial diagnosis and treatment of non- thyroid malignancy. Patients can present with enlarging thyroid nodules, neck swelling, dysphagia and, in rare instances, upper airway obstruction. We present a rare case of lung cancer with metastasis into the thyroid. The thyroid nodule initially palpated upon physical exam led to eventual thyroid ultrasound and subsequently to his diagnosis of lung adenocarcinoma after findings of lung nodule which was biopsied and showed primary lung adenocarcinoma. TTF-1 was also positive which is typically expressed by lung adenocarcinomas. Treatment for thyroid metastasis is surgery, along with treatment of primary malignancy. The earlier the diagnosis and treatment the more favorable the prognosis. Radiotherapy and chemotherapy are other means to reduce the recurrence. Thyroid hormone replacement will be warranted post operatively for hypothyroidism. We present this uncommon case to raise awareness about the presentation of thyroid metastasis to enhance timely diagnosis and intervention. Presentation: 6/1/2024

7618 Thyroid Nodules, Normal Thyroid Levels, and Chronic Anxiety: A Case for Sub-Clinical Toxic Multinodular Goiter

Abstract Disclosure: C.M. Barrera: None. Introduction: Chronic anxiety and panic disorders, as described in the Diagnostic and Statistical Manual of Mental Disorders (DSM-V), are the most common psychiatric conditions. Hyperthyroidism is a known cause of both chronic anxiety and panic disorder. Case 1: A 36-year-old overweight Latin female is referred for evaluation of multiple thyroid nodules. The thyroid ultrasound was heterogeneous, with multiple bilateral nodules. In her history, the patient has chronic anxiety with panic attacks resulting in frequent emergency room visits. The TSH and T4 levels were TSH 0.59 mIU/L (0.40-4.5) and T4 10.7 mcg/dL (5.1-11.9). An I[1]23- Thyroid Scan showed a hot nodule with mild suppression and an uptake of 31.8% (The top limit is 35%). The patient started methimazole 2.5 mg daily, and after two months, her chronic anxiety and panic attacks resolved. Post-methimazole TSH rose to 1.18 mIU/L, and T4 10.0 mcg/dL and she has weaned off anxiety medications. Case 2: A 49-year-old overweight Latin female is referred for increased thyroid nodules. She complained of six months of tachycardia and anxiety. The TSH and T4 levels were TSH of 0.828 mIU/L (0.40-4.5) and T4 of 7.9 mcg/dl (4.5-12.0). An I[1]23-Thyroid Scan showed no dominant hot or cold nodules, with an uptake of 36.4% (The top limit is 35%, within normal error limits). She started methimazole 5 mg daily, resolving her tachycardia and anxiety within five weeks. Post-methimazole TSH was 1.64 mIU/L (0.45-4.5), and T4 6.7 mcg/dL (4.5-12.0). Case 3: A 60-year-old overweight Latin female is referred for evaluation of multiple thyroid nodules of ten years. She complained of chronic anxiety and panic attacks for two years. The TSH and T4 were normal at TSH 0.36 mIU/L (0.35- 5.50) and T4 9.7 mcg/dL (4.5-10.9). The thyroid ultrasound showed multiple bilateral nodules. An I[1]23-Thyroid Scan showed a suspected hot nodule without appreciable suppression and an uptake of 33% (The top limit is 35%). The patient started methimazole 5 mg daily. After eight weeks, she reported the resolution of most of her chronic anxiety with post-methimazole TSH 2.39 mIU/L and T4 7.1 mcg/dL (4.5-12.0). Discussion: The normal range of TSH, typically from 0.4-4.5 mIU/L, is calculated by measuring the TSH levels among a normal population. The group range then determines the laboratory reference range. This contrasts with individual values, which have a narrower range, suggesting that each person has a unique thyroid level. This suggests that TSH levels at the extremum, associated with hyperfunctioning nodules contributing to a rise in uptake, may not be normal for that patient and may explain the anxiety and other symptoms. Learning Points: Evolving multiple autonomous thyroid nodules lowers TSH levels while raising thyroid uptake. Symptoms of chronic anxiety and panic attacks can predate abnormal thyroid levels and resolve with low-dose methimazole. Presentation: 6/1/2024

8791 A Case of Hyperfunctioning Thyroid Nodules Evaluated for Thyroid Metastasis in the Setting of Oropharyngeal Squamous Cell Carcinoma

Abstract Disclosure: M. Alashoor: None. J. Gogineni: None. A. Bakar: None. Introduction: Identifying and evaluating hyperfunctioning thyroid nodules in the setting of metastatic head and neck cancers represents a diagnostic challenge that may result in inaccurate identification of perithyroidal lymph node metastasis as malignant or metastatic thyroid nodules with standard workup. Case presentation: A 72-year-old male with a history of stage IV metastatic oropharyngeal squamous cell carcinoma, metastasized to the lymph nodes, lungs, mediastinum, and bilateral iliac bones. He was diagnosed two years ago and received chemotherapy, maintenance immunotherapy with pembrolizumab, and targeted palliative radiation therapy, with good clinical response. Restaging PET-CT two years later revealed local progression. During his workup, he was noted to have persistently abnormal thyroid function test with low TSH (0.03​​µIU/mL, n 0.3-5.33), normal free T4 (0.97ng/dL, n 0.60 - 1.40), mildly elevated free T3 (3.91pg/mL, n 2.5-3.9), negative thyrotropin receptor antibodies levels, negative TSI, negative TPO antibody, noted evidence of subclinical hyperthyroidism consistent over the past year. Radioactive iodine uptake demonstrated multinodular gland, mildly elevated 24-hour uptake of 28% consistent with hyperthyroidism, with decreased activity in the left lobe. Thyroid ultrasound revealed multiple probable malignant thyroid nodules, a 1.8 cm TI-RADS 5 lesion of the deep margin of the lower pole of the right lobe, and a 1.6 cm TI-RADS 5 lesion of the upper pole on the right lobe. He was treated with methimazole 5 mg. Further workup with fine needle aspiration demonstrated the right upper lobe nodule sample was positive for squamous cell carcinoma, findings suspicious for metastasis. He subsequently proceeded with radical tonsillectomy, right neck dissection, and right hemithyroidectomy. Surgical pathology results noted, right neck metastatic HPV-associated squamous cell carcinoma involving the lymph nodes with extranodal extension, right oropharyngeal HPV-mediated squamous cell carcinoma. The thyroid gland biopsy was significant for incidental papillary microcarcinoma 2mm, thyroid follicular nodular disease, without evidence of squamous cell carcinoma or metastatic infiltration. Post-hemithyroidectomy, his thyroid function normalized, and methimazole was discontinued. Conclusion: Thyroid metastasis from head and neck cancers represent a rare entity. In patients with a history of malignancy, evaluation of new thyroid masses remains crucial. While FNA is a sensitive method for detecting thyroid metastases, inaccuracies may occur, impacting the identification of thyroid nodules in the presence of local metastatic lymphadenopathy. Identifying squamous cell carcinoma in the thyroid can significantly influence the treatment plan of patients with metastatic carcinomas, therefore careful consideration must be undertaken on evaluation. Presentation: 6/1/2024

6641 Observation in Lieu of Surgical Management in Hurthle Cell Neoplasm: Role of Thyroseq V3 Molecular Testing

Abstract Disclosure: R. Kaur: None. L. Kaur: None. T. Chaudhary: None. M. Shrivastava: None. N. Patel: None. The diagnostic utility of fine needle aspiration biopsy with cytology is often confounded in thyroid nodules with predominance of hurthle cells, often interpreted as an oncocytic/hurthle cell lesion with intermediate risk of malignancy, bethesda category (BC) III or IV. With the advent of molecular testing like thyroseq V3, it is helpful in ruling out substantial risk of cancer and considering observation in lieu of surgical management in such difficult cases. We present a case of a 75 year old woman with past medical history significant for type 2 diabetes mellitus and hypothyroidism who was found to have a left lobe complex nodule within a non-toxic multinodular goiter In 2022. Ultrasound of the neck showed a 1.6 x 1.8 x 2 cm intermediate nodule, followed by a fine needle aspiration biopsy which was non-diagnostic and reported as benign, showing only cystic contents and insignificant follicular cells, Bethesda class II. Follow up for the nodule was recommended in one year. Repeat Imaging one year later revealed left nodule without significant changes and repeat fine needle aspiration cytology was advised. The biopsy result was reported as an oncocytic/ Hurthle cell neoplasm, Bethesda class IV. The specimen was also submitted for thyroseq molecular testing and results were awaited. The patient was euthyroid with negative anti thyroid antibodies. There was no family history of thyroid cancer or radiation exposure. The patient denied any active symptoms like shortness of breath, neck pain or pressure, recent voice changes, dysphasia, loss of appetite or weight .On examination the patient was found to have a left thyroid nodule with no signs of tracheal deviation. CT scan of the neck demonstrated a left thyroid nodule with no compression. The patient was followed by both endocrinology and oncology and surgical options were discussed depending upon the biopsy results while awaiting molecular testing report. Molecular testing with thyrosec V3 revealed an absence of gene mutations and reported a low probability of cancer. Depending upon the results observation was considered in lieu of surgical management. Hence It was decided to keep the patient under observation considering the molecular test results in conjunction with all relevant imaging, clinical findings, symptoms, patients family history as well as patients preference. This case report demonstrates the crucial role of molecular Diagnostics specifically thyroseq V3 in the often difficult clinical management of hurthle cell thyroid nodules for ruling out surgical management. Thyroseq V3 shows reliable performance in Hurthle cell cancers with sensitivity of 93% and specificity of 69%. In times of patient guided decision making and ability to narrow down the need of surgery based on pre-operative fine needle aspiration cytology, molecular profiling of thyroid nodules has become increasingly utilized. Presentation: 6/1/2024

8414 Utilization Of Cell Free DNA Integrity Index To Differentiate Benign From Malignant Thyroid Nodules

Abstract Disclosure: S. Tarafdar: None. S. Dutta: None. P. Mukhopadhyay: None. N.P. Bhattacharya: None. S. Ghosh: None. Introduction: Recent advances in molecular genetics have evaluated a potential role for plasma cell-free DNA (cfDNA) integrity index as a non-invasive cancer marker. Data on cfDNA integrity in differentiated thyroid cancer is sparse and needs to be investigated further. Aim of the study: The purpose of this study is to investigate the hypothesis that longer DNA strands in plasma may serve as a marker for thyroid cancer. Methods: Patients presenting with thyroid nodules underwent ultrasonography with Thyroid Image Reporting and Data Systems (TIRADS) scoring and FNAC (Bethesda classification).Patients with Bethesda 3, 4, 5, and 6 had surgery and confirmation by histopathology. Patients with Bethesda 2 presenting with compressive symptoms and cosmetic concerns underwent surgery; the remaining patients were considered benign based on clinical follow-up, USG, and FNAC characteristics. Blood sample collected prior to FNAC was used to extract and quantify cfDNA. To assess the integrity index 180/67, 306/67, and 476/67 for the APP gene, we used a quantitative real-time PCR (qPCR) method based on the quantification of four amplicons of varying lengths (67, 180, 306, and 476 bp, respectively). Because culture cells had extremely intact genomic DNA, the genomic DNA obtained from the MDA-T32 papillary thyroid cancer cell line was utilised as a reference to estimate the relative DNA strand integrity in plasma DNA. To determine the (ΔCt) value for 67,180, 306, and 476 bp, the Ct value of the sample was subtracted from that of the MDA-T32 control. Results: A total of 161 subjects were recruited, of these 92 were benign and 69 had differentiated thyroid cancer(confirmed by histopathology). Using the 180/67 bp integrity index benign thyroid nodule patients had significant lower value (median 0.39, 95% CI: 0.33-0.46) compared to patients with differentiated thyroid cancer (median 0.62, 95% CI: 0.56-0.68). A cfDNA integrity index of 180/67 bp could significantly differentiate between benign and malignant thyroid nodules (P<0.001). However, there was no significant difference between malignant and benign thyroid nodules based on the cell free DNA integrity indexes of 306/67 and 476/67. Conclusions: The cfDNA integrity score of 180/67 exhibits potential as a circulating marker for the detection of thyroid nodules and as a means of monitoring cfDNA fragmentation in patients with thyroid cancer. However, further confirmation through prospective trials is necessary. Presentation: 6/3/2024

8578 Papillary Thyroid Carcinoma in Autonomous Nodule with Low Risk Characteristics in Adolescent

Abstract Disclosure: A. Aponte Velez: None. M.M. Mangual Garcia: None. Thyroid nodules in children are uncommon but are known to carry a greater risk of malignancy than adult thyroid nodules. Additionally, differentiated thyroid cancer (DTC) in children is more commonly found with extrathyroidal extension and metastases which makes the approach and treatment similar but with important differences. The incidence of DTC in children is increasing, making a personalized evaluation of thyroid nodules in pediatric patients even more valuable. Guidelines recommend evaluation of nodules based on sonographic characteristics rather than size of nodule. However, not having worrisome sonographic characteristics may not be as reassuring as in adult patients. A 13 year old female patient presented with a palpable non tender right sided solid thyroid mass. She had no family history of thyroid cancer or history of irradiation. Thyroid function tests were remarkable for TSH:0.017 and positive thyroid stimulating immunoglobulin. Thyroid Ultrasound findings described heterogenous parenchyma with multiple discrete lesions on right thyroid lobe with a dominant solid isoechoic nodule at upper lobe measuring 2.1 x 3.5 x 1.9cm and a smaller nodule in lower lobe. Thyroid scan demonstrated a large functional hot nodule occupying most of right thyroid lobe with suppression of rest of thyroid parenchyma. Ultrasound guided FNA was performed of this lesion and results were negative for malignancy. Patient underwent total thyroidectomy with pathology report revealing right thyroid nodule encapsulated classical variant of papillary thyroid carcinoma. No lymph node metastases were identified. Non neoplastic thyroid parenchyma revealed chronic lymphocytic thyroiditis. Patient underwent radioiodine therapy with Whole Body Scan post radioiodine therapy demonstrating focal increased radionuclide localization at in region of neck consistent with functional thyroid tissue. There was no evidence of metastatic disease. In children, risk of malignancy is underestimated in ultrasonography and cytology. In this patient, papillary thyroid carcinoma was identified despite being stratified as having low risk of malignancy based on ultrasonography characteristics, hyperfunctioning nodule in scintigraphy study along with negative FNA results. Hyperfunctional nodules are usually reassuring for low risk of malignancy but rarely DTC can be found as in our patient. Guidelines agree that FNA is not recommended in functional nodules as surgical resection is the main therapy in children. However, surgery may be deferred if subclinical hyperthyroidism and low risk sonographic characteristics are present such as in our patient. If surgery had been deferred, based on low risk of malignancy, the risk of progression of disease would have been higher. Prognosis of DTC in children is good but the recurrence rate along with morbidity at such a young age may improve with more studies of DTC in children. Presentation: 6/2/2024

7510 Use Of Tumor Markers And Surgery In The Management Of Medullary Thyroid Cancer During Pregnancy

Abstract Disclosure: M. Garver: None. C. Vaz: None. Introduction: Thyroid cancer is the second most diagnosed cancer during pregnancy, predominantly differentiated thyroid malignancies. [1] MTC during pregnancy is rare and challenging to manage due to its aggressive nature. We describe the successful diagnosis and management of MTC during pregnancy. Clinical Case: A 28 yo woman presented with a rapidly growing neck lump for 2 months with an associated unintentional 10lb weight loss and without compressive symptoms. She had no history of childhood radiation exposure or family history of thyroid cancer. Physical exam revealed a hard L lobe thyroid nodule without palpable lymphadenopathy. The patient was 5 weeks pregnant at the time. A neck US revealed a 4.2x2.7x2.0 cm L solid isoechoic thyroid nodule with punctate echogenic foci and microcalcifications. The nodule was classified as TIRADS 4 and ATA high suspicion. FNA noted Bethesda IV with positive IHC stains for chromogranin and calcitonin. Afirma MTC classifier was positive, confirming diagnosis of MTC. At 7 weeks gestation, calcitonin was markedly elevated at 3508 pg/mL (n <5 pg/mL), CEA 29.5 ng/mL (n <2.5 ng/mL) and calcium 10.3mg/dL (8.6-10.2mg/dL). Plasma normetanephrines were elevated to176 pg/mL (n <148 pg/mL) with normal metanephrines 28 pg/mL (n <57 pg/mL) and normal 24-hour urine metanephrines. CT neck revealed 3.2x2.8cm L thyroid nodule without cervical lymphadenopathy. Due to pregnancy status, additional imaging to assess for metastatic disease was deferred until after delivery. Genetic testing did not identify mutations within the thyroid cancer panel including APC, CHEK2, DICER1, MEN1, PRKAR1A, PTEN, RET, SDHB, SDHD, and TP53. The patient underwent total thyroidectomy with neck dissection at 19 weeks gestation without complication. Two weeks postoperative Calcitonin was 2 pg/mL(n <5 pg/mL) and CEA was undetectable. Conclusions: The effect of pregnancy on MTC is not well studied because of low incidence. Guidelines on the timing of surgery for MTC diagnosed during pregnancy are lacking. While evidence confirms that surgery can be safely postponed until after delivery for low risk differentiated thyroid malignancies, there is no consensus on timing of surgery for MTC. Given the aggressive nature of MTC, along with marked elevation of calcitonin and CEA in this case, surgery was performed in the 2nd trimester with excellent outcome. Data is conflicting on accuracy of calcitonin and CEA during pregnancy, with some reports suggesting falsely high levels due to pregnancy. The sharp decline in calcitonin and CEA 2 weeks postoperatively suggested these were truly elevated due to MTC and unaffected by pregnant status. We suggest that calcitonin and CEA be followed similar to non-pregnant cases with MTC. Resources: 1.Khaled, H. M., Lahloubi, N. A., & Rashad, N. (2016). A review on thyroid cancer during pregnancy: Multitasking is required. Journal of Advanced Research, 7(4), 565–570. Presentation: 6/2/2024

6925 A Rare Case of Metastatic Papillary Thyroid Carcinoma Confined to Cervical Lymph Node with No Identifiable Primary Tumor In The Thyroid Gland. A Diagnostic Conundrum

Abstract Disclosure: R. Abdelmasih: None. W. Pan: None. Introduction: Papillary thyroid carcinoma (PTC) is the most common treatable thyroid cancer (TC) with very good prognosis. Metastatic PTC either in the lymph node LN or extra-nodal with no primary thyroid lesion identified is a rare phenomenon referred to as occult thyroid carcinoma (OTC). Despite its rarity, it is reported and constitute a diagnostic conundrum. herein we present a case of metastatic PTC identified in cervical lymph nodes (LN) without a primary tumor in the thyroid gland confirmed with surgical pathology. Case Presentation: A 43-year-old female with history of post-ablative hypothyroidism after treatment of toxic nodular goiter for 10 years, with no family history of thyroid cancer presented with incidentally found left 1.8 Heterogeneous hypoechoic solid nodule with lobulated borders and internal calcifications along with left-sided 0.8 LN without normal fatty hilum on Ultrasound Head and Neck. Fine needle aspiration of the left thyroid nodule and suspicious LN revealed PTC in the left LN though the thyroid nodule sample was non-diagnostic. CT of head and neck showed partially calcified thyroid nodule, Hyperattenuating 8 mm left III LN without fatty hilum, and 9 mm left II calcified LN. Patient underwent total thyroidectomy, central neck, and left lateral neck dissection. Surgical pathology showed no malignancy in thyroid gland or central LNs and 1 out 5 LN of the left neck dissection showed PTC with tumor grading of pT0 pN1b pMNA. patient underwent whole-body thyrogen-stimulated thyroid scan which showed iodine avid tissue in the thyroid bed followed by high-dose I-131 radioactive iodine ablation (RAI). Discussion: OTC refers to impalpable incidental TC less than 10 mm per the WHO. Boucek et al classify OTC into four categories, recently a fifth category was added, in which metastasis is confirmed either in regional LN or distant metastasis though thyroid tissue is confirmed to be benign per pathology and imaging evaluation, our patient falls in the fifth category. Hypothesis of this phenomenon is not well understood, one suggested explanation is missed diagnosis due to not enough sample or if lesion is less than 3 mm. another hypothesis is tumor spontaneous regression, or regression secondary to treatment that was inadequate to treat the systemic process of the tumor, which we believe our patient fits in this hypothesis, given that she underwent RAI ablation many years ago. Tumor regression is very rare and reported to be 1 in 140,000 cases. Another theory suggests that PTC can arise in ectopic thyroid tissue. This case is to shed light on a rare clinical and pathological entity to avoid missed diagnoses. Prognosis depends on the extent of metastasis, with favorable one when it is limited to regional LN and worse with distant metastasis. More cases reports are warranted to help guide further management of such cases due to the lack of available guidance in use of RAI surveillance and ablation. Presentation: 6/1/2024

8049 Beyond Metastasis: Parasitic Thyroid Tissue Mimicking Thyroid Cancer

Abstract Disclosure: M.S. Shah: None. S. Humayon: None. N.A. Mungo: None. This case study details a complex clinical scenario involving a patient with diaphoresis and a familial history of thyroid cancer. Initial suspicions of functionally active metastatic thyroid cancer led to a thyroidectomy and cervical lymph node dissection, only to reveal unexpected parasitic thyroid tissue. This case highlights the importance of meticulous evaluation and follow up similar presentations, shedding light on the rarity of this phenomenon.The patient, experiencing a year of diaphoresis unresponsive to estradiol therapy, underwent imaging revealing multiple thyroid nodules. A left superior nodule (TI-RADS 4) and a more concerning right mid-posterior nodule (TI-RADS 5) prompted fine needle aspiration (FNA). FNA of the right thyroid nodule exhibited Bethesda category III atypia, no molecular samples were taken at that time, while cervical lymph node FNA yielded nondiagnostic results.Subsequent ultrasound showed no interval change in the right thyroid nodule but raised concerns about increased solid components and decreased echogenicity in other nodules. Due to patient concerns of positive family history of thyroid cancer, the lymph node was biopsied. The result yielded a low cellular sample, but follicular thyroid tissue was present. The patient elected to undergo thyroidectomy as she did not want to continue monitoring. Pathology revealed parasitic thyroid tissue in the lymph node and nodular follicular thyroid disease, with no evidence of papillary thyroid carcinoma in the gland. Notably, the patient had no history of thyroid surgeries, ruling out traumatic rupture or implantation from a follicular adenoma. However, the possibility of follow-up metastatic follicular carcinoma cannot be entirely excluded on histologic grounds.Follow-up tests were recommended, encompassing mutational analysis, whole-body scans, and thyroglobulin (Tg) monitoring. Molecular analysis did not favor cancer. Tg levels remained at (18 ng/ml, n< 35ng/ml) of initial evaluation six weeks post surgery and repeat testing is pending. Ablative radioactive iodine therapy may be appropriate as resection of all parasitic thyroid tissue can prove difficult.This case emphasizes the diagnostic challenges posed by the rare occurrence of parasitic thyroid tissue, often mistaken for metastatic thyroid cancer. The findings contribute to our understanding of uncommon thyroid pathologies. The clinical implications of this case extend to the importance of heightened clinical suspicion in intricate endocrine cases. Presentation: 6/3/2024

6689 A Multicentric Study for Validation of the Diagnostic Accuracy of ACR-TIRADS in a Mexican population

Abstract Disclosure: M. Romero Ibarguengoitia: None. I.A. Villarreal-Ondarza: None. J. Mercado Basurto: None. A. González Cantu: None. The diagnostic performance of ultrasonographic ACR-TIRADS classification to evaluate thyroid nodules is poorly studied in a Mexican population. The aim was to assess the diagnostic accuracy of ACR-TIRADS classification for identifying malignant thyroid nodules in adults aged >18 years. This retrospective research study was conducted in 4 medical centers in Northern Mexico from 2022 to 23 to obtain ACR-TIRADS classification of nodules from thyroid ultrasound. Information about Bethesda classification after fine needle aspiration and cytology from thyroidectomy was analyzed for diagnostic performance tests. A total of 160 patients were included. Thyroid nodules were classified as TIRADS 3 in 12%, TIRADS 4 in 44%, and TIRADS 5 in 41%. Twenty-six (16%) were classified as Bethesda 1, 39 (24%) were classified as Bethesda 5, and 30 (19%) were classified as Bethesda 6. The sensitivity (S) of TIRADS 4 was 41%, specificity (E) was 50%, positive predictive value (PPV) was 59%, negative predictive value (NPV) was 32%, and accuracy was 44%. The S of TIRADS 5 was 51%, E 77%, PPV 80%, NPV 47%, and accuracy of 61%. When comparing with other populations, the performance was the same as the Turkish (their accuracy was 59.93%) population but lower than a population from China (their accuracy was 86%) and Germany (PPV 100% for TIRADS 5). The proportion of malignancy in our sample compared with a reference sample from Germany was lower, 36 vs. 85% for TIRADS 3, 59 vs. 85% for TIRADS 4, and 80% vs. 100%, p< 0.001. Concerning Bethesda's classification, the proportion of malignancy was the same according to the reference sample from the American Thyroid Association. In conclusion, there was a moderate accuracy of the ACR-TIRADS classification system in our population, the same in comparison with the Turkish population; slightly lower than what is reported in a population from Germany and China. Presentation: 6/1/2024

6913 Clinical Prognosis in Patients with Thyroid Nodules Expressing PPAR-Gamma Gene Fusion on Thyroid FNA Cytology

Abstract Disclosure: R. Hammoudeh: None. E. Morariu: None. A. Wald: Other; Self; Technical consultant to Sonic Healthcare USA.. W.R. Doerfler: None. Y. Linwah: None. M. Nikiforova: Owner/Co-Owner; Self; Owner of intellectual property related to ThyroSeq, receive royalties through the University of Pittsburgh; consultants for Sonic Healthcare USA. Y.E. Nikiforov: Owner/Co-Owner; Self; Owner of intellectual property related to ThyroSeq, receive royalties through the University of Pittsburgh; consultants for Sonic Healthcare USA. Background: PPARG rearrangements, typically PAX8-PPARG, are common genetic alterations in follicular thyroid carcinoma and follicular variant of papillary thyroid carcinoma (FVPTC). Most tumors appear to be indolent, however distant metastasis has been reported. The aim of this study was to determine the prevalence and type of malignancy in a series of thyroid nodules positive for PAX8 rearrangement in thyroid fine-needle aspiration (FNA) samples. We also aimed to evaluate the impact on patient management, prognosis and outcomes. Methods: Thyroid nodules positive for PAX8 fusion on ThyroSeq v2 and v3 genomic classifier testing of FNA samples from May 2008 to February 2022 were identified. Clinical data was obtained by retrospective chart review. Results: Overall, 44 nodules positive for PAX8/PPARG fusion were identified. None of these nodules expressed additional genetic mutations on molecular testing. Surgical pathology was available for 40 patients, which identified 35 (87.5%) malignant, 3 NIFTP (7.5%), and 2 benign (5%) lesions. In the malignant group, FNA cytology revealed 1 (2.8%) benign, 13 (37.1%) AUS/FLUS, 12 (34.2%) suspicious for SFN/FN, 5 (14.3%) suspicious for PTC and 4 were not classified. In the non-malignant group, FNA cytology revealed 2 (40%) benign, 2 (40%) AUS/FLUS, 1 (20%) SFN/FN. With regards to surgical intervention, 30 (75%) patients had total thyroidectomy and 10 (25%) underwent lobectomy, of which 8 were followed by completion thyroidectomy. Among the malignant and non-malignant groups, there was no difference in sex (82.8% vs 100% female, p=1), age (43.6 vs 50.2 years, p=0.2), or tumor size on surgical pathology (3.26 vs 4 cm, p=0.23). In the malignant group, histology showed 30 (85.7%) FVPTC, 2 (5.7%) conventional PTC, 2 (5.7%) follicular carcinoma and 1 (2.9%) solid variant PTC. Of the FVPTC group, 9 had oncocytic cell features, 3 focal solid patterns, and 1 showed focal solid growth and progression to poorly differentiated thyroid carcinoma. Only 1 showed lymphatic invasion, 10 showed angioinvasion. Following the ATA thyroid cancer risk stratification, 23 (65.7%%) had low risk, 9 (25.7%) intermediate risk and 3 (8.6%) high risk. 18 patients in the malignant group underwent RAI ablation. Average follow up for the malignant nodules was 49.7 months (0-170). 1 had suspected recurrence on thyroid ultrasound after a year. No evidence of distant metastasis was documented. Conclusions: The majority of thyroid nodules with PAX8/PPARG rearrangement found on FNA were cancers, predominantly follicular variant PTC, and some were benign or NIFTP. The majority were low risk, but intermediate and high-risk cancers with more aggressive histology, angioinvasion, and poorly differentiated cancer were also identified. While only one recurrence was identified on short follow-up, longer follow-up duration is required for better understanding the behavior of these tumors. Presentation: 6/3/2024

8012 A Severe Thrombotic Event Following Blood Thinner Interruption for Thyroid Fine Needle Aspiration Biopsy: A Case Report

Abstract Disclosure: V.A. Mendpara: None. P.P. Rao: None. M.V. Kellis: None. M.D. Lundholm: None. Background: This case highlights the potential severe thrombotic consequences of blood thinner medication interruption for thyroid fine needle aspiration (FNA). Case Presentation: A 77-year-old woman came to the endocrinology clinic for follow-up on thyroid nodules. She was a former smoker with controlled type 2 diabetes, hypertension, hyperlipidemia, and atrial fibrillation with patent foramen ovale on apixaban. She had no family history of thyroid cancer and no radiation exposure. Thyroid nodules were found incidentally, and she denied compressive symptoms. She had annual surveillance for the past 4 years, and her latest thyroid US redemonstrated 4 solid, hypoechoic nodules. The largest nodule, previously biopsied and benign in 2020, remained stable on the right. The next largest nodule in the left mid-thyroid was now 1.1 x 0.8 x 0.9 cm—a 30% growth from the previous year—with new punctate echogenic foci consistent with the TIRADS 5 classification. This finding was shared with the patient, who favored investigating with an FNA. At the recommendation of her PCP and the performing provider, she held her apixaban for approximately 48 hours before the FNA procedure.The US-guided thyroid FNA biopsy was uneventful, and the results indicated a benign nodule. However, 4 hours post-procedure, the patient suddenly became unresponsive while in the middle of cooking dinner. She was taken to the ED and found to have an ischemic stroke by basilar embolism, attributed to her interruption in apixaban therapy. Tenectaplase led to initial improvement but had subsequent hemorrhagic transformations affecting the midbrain, thalamus, and pons. This marked the beginning of a complex 2-month hospitalization requiring tracheostomy and percutaneous endoscopic gastrostomy (PEG) placement, followed by nearly a year of physical, occupational, and speech rehabilitation. Despite these efforts, she has not been able to return to her pre-stroke level of function and independence. Discussion: There is no consensus on the safety of performing a thyroid fine needle aspiration (FNA) biopsy for patients on blood thinner medications. Providers who favor holding blood thinners before FNA cite concerns for post-procedural hematoma formation or increased risk of non-diagnostic results. However, there is less discussion about the risks of interrupting these medications. This case emphasizes the potential for severe consequences from interrupting medically-indicated blood thinner therapy. The temporary discontinuation of apixaban for a routine thyroid FNA led to a life-threatening thrombotic event in our patient’s case. This outcome highlights the importance of carefully weighing the risks and benefits of medication interruptions for vulnerable populations. Further study is needed to investigate the safety of thyroid FNA on uninterrupted blood thinner therapy. Presentation: 6/2/2024

8113 Thyroid Storm in a Patient with Thyroid Nodule on Anticoagulation

Abstract Disclosure: R. Kulkarni: None. S.S. Krishnasamy: None. N. Mon: None. R. Downs: None. Background: There are very few case reports related to hyperthyroidism due to anticoagulation use. We describe a case, of a less common cause of hyperthyroidism due to hemorrhagic thyroiditis in a patient on anticoagulation and history of metastatic colon cancer. Clinical case: A 67-year-old white male with PMH significant for colon cancer with liver metastasis s/p exploratory laparotomy with sigmoid colectomy, end-colostomy with Hartman's pouch creation, pre-diabetes, recent left IJ & axillary vein thrombus on Eliquis, and thyroid nodule; presented with complaints of shortness of breath, difficulty swallowing and dizziness. Other symptoms included weight loss, complaints of heart racing and generalized body aches. The patient had a recent admission for similar complaints and was newly diagnosed with left IJ/axillary vein thrombus and expanding hemorrhagic thyroid nodule on imaging. He was discharged on anticoagulation for the DVT with 2 week follow up for elective thyroidectomy for goiter. The patient was admitted to the ICU for worsened respiratory status needing ventilatory support and pressor support. Physical findings on admission included jaundice, sinus tachycardia, lethargy with agitation. Initial labs showed TSH 0.02 uIU/mL, FT4 4.85 ng/dL and FT3 6.8 pg/mL, LFTs >500 U/L. Burch-Wartofsky Point Scale score was >60 suggestive of thyroid storm. Imaging with PET CT was concerning for thyroid enlargement with multiple nodules with increased uptake. Thyroid US was consistent with heterogenous gland with hemorrhagic nodules. Based on clinical history, physical findings, diagnostic labs, and imaging the patient was diagnosed with severe hyperthyroidism with thyroid storm secondary to hemorrhagic thyroid nodules in the setting of anticoagulation. The patient underwent thyroid artery angiogram with particle embolization of left inferior and right superior thyroid arteries. Endocrinology started the patient on methylprednisolone, cholestyramine and propranolol. Thionamide was held since the patient had abnormal liver function tests in the setting of shock liver. The patient’s thyroid function slowly improved on current regimen to TSH 0.05 uIU/mL, FT4 1.7 ng/Dl and FT3 4.1 pg/mL on day 3. At the family interdisciplinary meeting, due to guarded prognosis, family opted for comfort care, and the patient finally succumbed to multiple co-morbidities. Conclusion: The case presented discusses diagnosis and management of less common causes of hyperthyroidism and management of thyroid storm in liver dysfunction. The patient would have needed a thyroid biopsy at a later date to rule out colonic metastasis as a cause of hemorrhage if he had survived the thyroid storm and comorbid illnesses. Presentation: 6/3/2024

8760 Does an Increased Size of Thyroid Nodules Correlate with a Higher Probability of Intermediate or High-Risk Histopathological Features for Recurrence?

Abstract Disclosure: R. Pishdad: None. N. Yousefzadeh: None. E. Gough: None. L. Rooper: None. J.S. Mammen: None. Does an increased size of thyroid nodules correlate with a higher probability of intermediate or high-risk histopathological features for recurrence? Background: The existing practice guidelines recommend total thyroidectomy for solitary nodules exceeding 4 cm regardless of other pre-operative findings. We hypothesize that through comprehensive pre-operative assessments, particularly including a thorough neck ultrasound, even nodules exceeding 4 cm that would otherwise meet ATA criteria for lobectomy (i.e., lacking extrathyroidal extension and suspicious lymphadenopathy) will not exhibit occult high-risk features at a higher rate compared to nodules measuring 1-4 cm. Consequently, these larger nodules would not necessitate a higher rate of completion thyroidectomy. Methods: Solitary thyroid nodules with a largest dimension ≥ 1 cm and operated on at a single institution between 2005 to 2023 were assessed to identify those that would have met ATA criteria for lobectomy. Surgical pathology reports were reviewed to perform risk stratification following ATA guidelines. Preoperative cytopathology, ultrasound characteristics, and patient demographics were considered as covariables. Statistical analyses were performed with R programming language. Simple logistic regression and multivariable logistic regression were performed to analyze the finding of occult intermediate or high-risk features based on size. Results: We identified 461 cases of solitary nodules without extrathyroidal extension or lymph node involvement (406 nodules 1-4 cm; 60 nodules ≥ 4 cm). Patients with larger nodules were more likely to be male than those with smaller nodules (52% versus 26%; P value <0.001). Interestingly, while the majority of smaller nodules meeting criteria for lobectomy were suspicious or malignant by cytopathology (Bethesda 5 and 6), only 20% of larger nodules that met criteria were malignant, with 68% either Bethesda 3 or 4 (p<0.001). There were no statistically significant associations between size or other variables such as age, race, sex, or positive family history and post-operatively assessed high/intermediate risk for recurrence. Conclusion: In this analysis of solitary nodules with larger sizes, the dimension itself did not emerge as a risk factor for occult intermediate or high-risk surgical pathology. Thus, the rates of completion thyroidectomy in appropriately screened patients would be acceptable even in patients with nodules greater than 4 cm. The majority of larger nodules that fulfill preoperative ATA criteria for lobectomy were assessed to be ACUS or a follicular neoplasm on pre-operative fine-needle aspiration. This suggests that the higher risk of more aggressive disease previously reported with larger nodules can be detected during preoperative assessment, emphasizing the essential role of neck US in the comprehensive evaluation of larger nodules. Presentation: 6/2/2024

8373 High suspicion for thyroid cancer in patient with thyroid Hemiagenesis

Abstract Disclosure: L. Aoun: None. S. Almardini: None. M. Anise: None. F. Haddadin: None. F. Saliba: None. J. Zaidan: None. Background: Thyroid Hemiagenesis (THA) is a rare condition characterized by congenital absence of one lobe of the thyroid gland. Notably, THA is more prevalent in females and the left lobe is more likely to be absent with or without the isthmus. Most patients are euthyroid, and diagnosis is usually incidental, so the true prevalence of THA is uncertain as there are certainly undiagnosed cases. Studies have shown a link between THA, thyroid cancer, and hyperparathyroidism. We present a case of THA and high suspicion for thyroid cancer. Case Presentation: 54-year-old female with history of Rheumatoid arthritis who presented for evaluation of incidental thyroid nodules, occasional palpitations, tremors, and mild change in her voice. She denied abnormal weight loss or diarrhea. No history of radiation to the neck and no family history of thyroid disease or thyroid cancer. The thyroid exam showed an enlarged left palpable nodule. Labs significant for TSH 1.6 mIU/L (normal: 0.4-4 mIU/L), FT4 0.8 ng/dl (normal 0.7-1.9 ng/dL) and T3 77ng/dL (normal: 60-180 ng/dL). Thyroid U/S showed left hemiagenesis and right sided nodules biggest is 1.1 cm solid, hypoechoic with coarse calcifications, FNA was recommended and showed follicular lesion of undetermined significance, molecular testing was done and Thyroseq came back intermediate to high risk RAS and EIF1AX positive reflecting a 70 % probability of cancer. Based on these results, surgery was recommended, and the patient underwent right thyroidectomy. Surgery was uncomplicated and despite reported higher risk of hyperparathyroidism patient’s calcium and PTH were normal, and no parathyroid adenomas were identified intraoperatively. The pathology from the thyroidectomy showed follicular adenoma of 1 cm and no malignancy. She was started on Synthroid 100mcg daily post op. Discussion: This case demonstrates a case of a benign thyroid nodule and preserved parathyroid levels in the setting of thyroid hemiagenesis. Usually in THA, the contralateral lobe is at an increased risk for pathology of compensatory hypertrophy or hyperplasia. According to available studies, cancer association with THA was more common in left hemiagenesis and parathyroid adenomas more common ipsilateral to hemiagenesis . Despite Our patient’s FNA revealed atypical findings, molecular testing revealed RAS and EIF1AX positive, marking intermediate to high cancer risk. However, the thyroidectomy pathology report unveiled no evidence of malignancy, contraindicating the anticipated high cancer risk in those with left THA. This case highlights the rarity of THA and different possible presentations and cancer risks. Presentation: 6/2/2024

8728 Radiofrequency Thermal Ablation in Thyroid Microcarcinomas: Experience of the Brazilian Group with 143 Cases

Abstract Disclosure: L.G. Amato: None. P.H. Carani: None. L.D. Volpi: None. A. Rahal: None. E.M. Volpi: None. Introduction: Thyroid nodules are quite prevalent worldwide, with papillary thyroid carcinoma (PTC) being the most common histological subtype of thyroid malignant neoplasm, accounting for approximately 85% of thyroid cancers. When this carcinoma is less than 10 mm in its longest axis, it is defined as papillary thyroid microcarcinomas (mPTCs) which has had an increasing proportion of thyroid cancers and with a disease-specific survival of patients having this diagnosis more than 99% after 10 years of follow-up. Most guidelines concerning thyroid cancer care recommend a lobectomy as the first-line treatment strategy for low-risk unifocal mPTC but often results in aggressive overtreatment. Thyroid surgery comes with significant costs and morbidity rates caused by iatrogenic hypothyroidism and recurrent laryngeal nerve damage, resulting in poor quality of life, justifying the growing search for minimally invasive and effective methods in the treatment of mPTC and in this context Radiofrequency thermal ablation (RFA), a minimally invasive treatment that preserves thyroid function have been proposed for patients with low-risk mPTC. Clinical case: From April 2018 to January 2024, 143 patients with mPTC, were submitted to RFA and patient's follow-up were dated 1, 3, 6, 12 and 18 months after the procedure. During the follow-up we observed 3 (2%), complications, 1 case of permanent paralysis unilateral vocal cord, 1 Horner Syndromes and 1 case of transient paralysis, with total reversal. In all cases there was a reduction in the volume of the node after 6 months of the procedure. Conclusion: The reported incidence rate of postoperative hypothyroidism in patients underwent hemithyroidectomy is 10.9-48.8%, therefore, risks of complications with radioablation in our series were lower than those previously described during hemithyroidectomy. Radiofrequency thermal ablation (RFA) is a minimally invasive treatment that preserves thyroid function with a lower incidence of complications compared to thyroidectomy or lobectomy, and and should be considered the selection procedure for low-risk thyroid microcarcinomas. Presentation: 6/3/2024