Thyroid Lobe Research Articles

9365 Now You See Me: The Case Of The Ectopic Thyroid

Abstract Disclosure: S.I. Suarez: None. S.K. Majumdar: None. Introduction: Lingual thyroid refers to ectopic thyroid tissue located at the base of the tongue or within the thyroglossal tract secondary to failed descent to its usual site (1). Ninety percent of ectopic thyroid glands are found at the base of the tongue and can occur in 1 in every 100,000 patients (2, 3). Clinical presentations commonly relate to obstruction of the oropharynx, and patients may experience dysphagia or throat fullness/discomfort (1). We present a case of lingual thyroid presenting as dysphagia and progressive hypothyroidism. Case: A 38-year-old woman with a history of HLD and hypothyroidism was referred for evaluation of ectopic thyroid tissue. She presented to her provider for concerns of dysphagia, neck swelling, and excessive hair thinning/loss. She had a recent increase in levothyroxine dose from 112 to 125 mcg after a TSH of 20.4 (0.27 to 4.2 uIU/mL). Repeat tests showed a TSH of 29.4 and a free T4 level of 0.79 (0.8 to 1.7 ng/dL). She denied use of thyrotoxic medications, any radiation or surgeries to head or neck, personal or family history of autoimmune disorders. Thyroid was nonpalpable on exam. A thyroid US 5 years prior showed a 15 x 5 x 5 mm right lobe and 12 x 8 x 5 mm left lobe. CT scan of soft tissue of neck with contrast showed a 14 x 13 x 15 mm hyperintense nodular lesion midline along the anterior glossoepiglottic fold at the foramen cecum, with an 8 x 11 x 8 mm hyperintense nodular lesion at midline abutting the anterior body of the hyoid bone, and no thyroid tissue in the expected thyroid bed, findings consistent with ectopic thyroid tissue along the expected thyroglossal duct. Furthermore, an I-123 scan with SPECT confirmed the ectopic thyroid tissue. What was thought to be thyroid lobes on previous thyroid US was likely paratracheal fat. Levothyroxine was increased to 137 mcg per day with improvement at 2 months (TSH 10.4, Free T4 0.91). Adjusting levothyroxine replacement was the primary intervention, given that elevated TSH may result in hypertrophy of lingual thyroid tissue resulting in dysphagia, particularly if there is no mass or suspicion of cancer on imaging. Conclusion Hypothyroidism presenting with dysphagia in the absence of goiter, previous thyroid surgery, or detectable thyroid tissue should warrant consideration of ectopic thyroid tissue and initial therapy should be directed towards normalizing TSH in conjunction with excluding malignant causes.

5118 When Thyroid Gland Is Not Made Of Thyroid Cells

Abstract Disclosure: A. Bulut: None. L. Ma: None. J.P. Noordzij: None. S.Y. Lee: None. Introduction: Neurofibroma is a type of peripheral nerve tumor that can arise sporadically or be a part of neurofibromatosis type 1 (NF1), a rare genetic disorder. Neurofibromas within the thyroid gland are extremely rare. Here, we present the fifth reported case of primary neurofibroma of thyroid gland. Case: A 60-year-old woman with history of systemic lupus erythematosus and hypertension presented with enlargement of left thyroid gland. She was diagnosed with Graves’ disease 40 years ago, which was treated with right thyroid lobectomy one year after the initial diagnosis. Five years after the surgery, she had recurrence of her symptoms and received radioactive iodine ablation with subsequent hypothyroidism. On presentation to endocrine clinic, she had thyroid ultrasound (US), which showed surgically absent right thyroid lobe and enlarged heterogenous left thyroid lobe measuring 5.1 cm x 3.8 cm x 3.9 cm with scant blood flow without discrete nodules. In interim, patient developed dysphagia and globus sensation. Repeat thyroid US showed enlargement of left lobe to 5.6 cm x 3.7 cm x 4.7 cm. Patient underwent completion thyroidectomy. Surgical pathology showed neurofibroma (S-100+, CD34+ and MSA-) without any thyroid parenchyma. Whole-body scan revealed no other evidence of tumors. Patient was referred for genetic analysis. Discussion: Neurofibromas are benign peripheral nerve system tumors primarily consist of Schwann cells along with other components of perineurium. They can occur as a sporadic lesion which accounts for 90% of solitary neurofibroma cases or be a part of NF1 on rare occasions. NF1 is an autosomal dominant genetic disorder due to germline mutation in NF1 gene located on chromosome 17q11.2, whose manifestations include café-au-lait macules, Lisch nodules, skeletal abnormalities, neurological deficits, and other benign and malignant tumors. Neurofibromas are the hallmarks of NF1. There are only few cases in the literature reported neurofibromas adjacent to or originating from thyroid gland. To the best of our knowledge, there have been only four other cases reporting primary neurofibroma of thyroid gland, one of which developed from thyroid capsule. Our patient most likely has primary neurofibroma of thyroid gland given the lack of syndromic features, however, genetic testing is needed in order to rule out NF1. In conclusion, clinicians should consider neurofibroma in their differential in cases of enlarging thyroid gland or nodules, especially in the presence of other clinical features. Presentation: 6/1/2024

5118 When Thyroid Gland is Not Made of Thyroid Cells

Abstract Disclosure: A. Bulut: None. L. Ma: None. J.P. Noordzij: None. S.Y. Lee: None. Introduction: Neurofibroma is a type of peripheral nerve tumor that can arise sporadically or be a part of neurofibromatosis type 1 (NF1), a rare genetic disorder. Neurofibromas within the thyroid gland are extremely rare. Here, we present the fifth reported case of primary neurofibroma of thyroid gland. Case: A 60-year-old woman with history of systemic lupus erythematosus and hypertension presented with enlargement of left thyroid gland. She was diagnosed with Graves’ disease 40 years ago, which was treated with right thyroid lobectomy one year after the initial diagnosis. Five years after the surgery, she had recurrence of her symptoms and received radioactive iodine ablation with subsequent hypothyroidism. On presentation to endocrine clinic, she had thyroid ultrasound (US), which showed surgically absent right thyroid lobe and enlarged heterogenous left thyroid lobe measuring 5.1 cm x 3.8 cm x 3.9 cm with scant blood flow without discrete nodules. In interim, patient developed dysphagia and globus sensation. Repeat thyroid US showed enlargement of left lobe to 5.6 cm x 3.7 cm x 4.7 cm. Patient underwent completion thyroidectomy. Surgical pathology showed neurofibroma (S-100+, CD34+ and MSA-) without any thyroid parenchyma. Whole-body scan revealed no other evidence of tumors. Patient was referred for genetic analysis. Discussion: Neurofibromas are benign peripheral nerve system tumors primarily consist of Schwann cells along with other components of perineurium. They can occur as a sporadic lesion which accounts for 90% of solitary neurofibroma cases or be a part of NF1 on rare occasions. NF1 is an autosomal dominant genetic disorder due to germline mutation in NF1 gene located on chromosome 17q11.2, whose manifestations include café-au-lait macules, Lisch nodules, skeletal abnormalities, neurological deficits, and other benign and malignant tumors. Neurofibromas are the hallmarks of NF1. There are only few cases in the literature reported neurofibromas adjacent to or originating from thyroid gland. To the best of our knowledge, there have been only four other cases reporting primary neurofibroma of thyroid gland, one of which developed from thyroid capsule. Our patient most likely has primary neurofibroma of thyroid gland given the lack of syndromic features, however, genetic testing is needed in order to rule out NF1. In conclusion, clinicians should consider neurofibroma in their differential in cases of enlarging thyroid gland or nodules, especially in the presence of other clinical features. Presentation: 6/1/2024

12361 An Unusual Case of Myxedema Coma

Abstract Disclosure: N. Hasan: None. D. Yang: None. T. Othman: None. J. Dai-Ju: None. Background: Most cases of Myxedema Coma are associated with primary hypothyroidism with significantly elevated TSH levels. However the presence severe illness can contribute to decreased TSH release even in the absence of central lesions. Case: 60 year old female was found down covered in feces. She was hypothermic to 89°F, with a pulse of 62. Physical exam revealed hair loss, thick tongue, non-pitting edema, and delayed relaxation of brachial reflexes. Labs showed Sodium of 123, blood glucose of 80. Thyroid function testing revealed only a mildy elevated TSH of 13 with free T4 <0.025. Anti-TPO antibodies were elevated at 157. MRI of the Sella was negative any lesions. Thyroid ultrasound showed atrophic bilateral thyroid lobes. Assessment for hypopituitarism did not show any significant deficiencies with Cortisol 45, ACTH 11, LH 0.5, FSH 8.5, IGF-33, and Total Testosterone 10. She was found to have septic shock secondary to perforated sigmoid colon requiring colectomy. She was initially loaded with Dexamethasone 4mg followed by IV Levothyroxine 100mcg, with steroids being discontinued after AI was ruled out. After treating her sepsis she was transitioned to 150mcg of oral Synthroid with improvement of her thyroid function tests to TSH of 2.7 and free T4 of 1.56. Discussion: The majority of Myxedema Coma is associated with primary hypothyroidism. In these cases, TSH levels are markedly elevated, often greater than 100. When the TSH is not as elevated as we would expect, many factors must be considered, the greatest being central hypothyroidism where TSH secretion may be impaired from pituitary tumors, surgery, radiation, and other causes. Our patient however did not have any central lesions on imaging and was found to have anti TPO antibodies with atrophic thyroid lobes on ultrasound suggestive of primary hypothyroidism. This brings us to the effect of acute illness on the balance of thyroid hormones. Conditions such as sepsis stimulates elevations in inflammatory cytokines which disrupt the physiologic response to release TSH. Previous studies involving sepsis revealed the main cytokines implicated are TNF alpha, Interferon gamma, IL-1, and IL-6. The degree of inadequate TSH secretion is often times proportional to the severity of illness and improves after recovery from the illness. Conclusion: Our body's response to critical illness involves complex hormonal changes which affect the HPA axis and can decrease TSH secretion, even in myxedema coma without central lesions. Presentation: 6/1/2024

7205 Anaplastic Thyroid Carcinoma Presenting as New-Onset Thyrotoxicosis and Hypoparathyroidism in a Young Patient: A Diagnostic Dilemma between Hashitoxicosis and Anaplastic Thyroid Cancer

Abstract Disclosure: M. Sulehri: None. E.G. Bustamante: None. A. Elmaaz: None. A. Chaudhuri: None. Introduction: This case report explores the complex diagnostic challenges encountered in a young patient presenting with anaplastic thyroid carcinoma (ATC) manifested by thyrotoxicosis and hypoparathyroidism. Case report: A 29-year-old male who sought multiple emergency room visits for shortness of breath, was initially misdiagnosed with pneumonia. On the third visit, exacerbated respiratory distress led to intubation, CT of the neck and thyroid US unveiling an infiltrative mass centered within the region of the thyroid gland. Initial thyroid function tests showed TSH <0.02 uIU/mL, free thyroxine 6.91 ng/dL, and total T3 204 ng/dL indicating hyperthyroidism, promptly managed with Methimazole and beta blockade. Elevated TPO antibodies (194 unit/mL) were observed, whereas thyroglobulin antibodies and thyroid receptor antibodies were undetected. Concurrently, hypoparathyroidism was noted, marked by low calcium levels (7.9 mg/dL) with albumin of 3.4 g/dL (corrected Calcium 8.4), and low parathyroid hormone (PTH) (<6 pg/mL). Other labs showed ionized calcium 4.30 mg/dL, phosphate 4.6 mg/dL, magnesium 1.8 mg/dL, and vitamin D 54 ng/dl. The patient received calcium carbonate supplement, calcitriol and IV calcium gluconate. Thyrotoxicosis then transitioned to hypothyroidism and levothyroxine replacement therapy was initiated. Definitive diagnosis was delayed due to the patient's overall condition and a low suspicion of malignancy. Left thyroidectomy and tracheostomy were performed, revealing dense subplatysmal necrosis with tumor involvement of both thyroid lobes and isthmus with multiple enlarged nodes. Final surgical pathology confirmed the presence of anaplastic thyroid carcinoma. Due to poor prognosis, the patient was transferred to hospice care where the patient succumbed to his condition within a day. Conclusion: Anaplastic thyroid cancer is considered one the most aggressive and fastest growing tumors. Although it is usually seen in patients after the age of 60, we present a very rare case of ATC in a young patient in the third decade who was presented with infiltrative thyroiditis and hypoparathyroidism. The case underscores the importance of considering rare etiologies in patients with atypical clinical presentation. Presentation: 6/1/2024

7914 Staged Treatment with Radioiodine Following Lobectomy in a Case of High Risk Papillary Thyroid Carcinoma

Abstract Disclosure: L. Pathak: None. A. Sharma: None. K. Rao: None. M.G. Jakoby: None. Introduction: Radioiodine ([1]3[1]I ) is usually reserved for patients with differentiated thyroid carcinoma (DTC) who are at high risk of persistence or recurrence after thyroidectomy. We present a case of papillary thyroid carcinoma (PTC) with extrathyroidal extension managed by lobectomy and staged [1]3[1]I ablation of the contralateral lobe and metastases due to comorbidities that made oncologic resection prohibitive. Case Description: A 58-year-old male had a 2.2 cm focus of PTC in the left thyroid lobe that extended into extrathyroidal soft tissue, adjacent trachea, and completely compromised the left recurrent laryngeal nerve. Due to left vocal cord paralysis and subglottic tracheal stenosis, left lobectomy was performed but oncologic resection (total thyroidectomy and tracheal resection) was deferred. The patient underwent recombinant human TSH (rhTSH) stimulated treatment with 30 mCi (1.1 GBq) of [1]3[1]I for right thyroid lobe ablation followed 60 d later by 180 mCi (6.7 GBq) of [1]3[1]I to treat metastases. Response to treatment was incomplete, with unstimulated thyroglobulin level falling from 293.9 to 18.9 ng/mL 1 y after [1]3[1]I and CT of the neck notable for a 2.7 cm left thyroid bed mass with invasion of adjacent trachea and a 1.0 cm right paratracheal mass, both of which exhibited hypermetabolism on PET imaging and yielded cytology consistent with poorly differentiated thyroid carcinoma (PDTC). A cluster of left supraclavicular lymph nodes showed both hypermetabolism on PET and radioiodine uptake on rhTSH scan. This patient is being prepared for surgical resection of the left thyroid bed and right paratracheal tumors and left lateral lymph node dissection. Discussion: Radioiodine lobar ablation is an alternative to completion thyroidectomy in patients with an unexpected diagnosis of DTC after lobectomy, with a recent meta-analysis finding a success rate of 69%. No difference in thyroid cancer recurrence rates was found in nearly 500 matched pairs of patients undergoing completion thyroidectomy or radioiodine lobar ablation. Unfortunately, staged lobar ablation followed by high dose [1]3[1]I was not successful in treating this high-risk PTC patient. Cases of coexisting PTC and PDTC are reported, and [1]3[1]I treatment was unsuccessful at treating PDTC that was not apparent on postsurgical histopathology. This case indicates that surgery is preferable to staged [1]3[1]I treatment of patients with aggressive PTC, especially if there are no comorbidities that make total thyroidectomy a high-risk procedure. Presentation: 6/2/2024

9189 Medullary Thyroid Cancer Due To A Novel Ret Oncogene Mutation In A Patient On Glp-1 Receptor Agonist

Abstract Disclosure: K. Lamar: None. D. John: None. O. Faour: None. N. Meda: None. M. Kinaan: None. Introduction: Mutations in the RET oncogene have been associated with increased risk of endocrine neoplasia and Medullary Thyroid Cancer (MTC). We report the case of a patient who has a (c.3281G>A) RET mutation, previously reported as a variant of uncertain significance. Case: A 51-year-old lady presented to our endocrine clinic for routine management of hypothyroidism, type 2 diabetes mellitus, and obesity. She had been on liraglutide, metformin, glipizide, and basal insulin for several years with good diabetes management. She had also been on levothyroxine for more than 10 years. On physical examination, a right thyroid lobe nodule was palpated. We performed a neck ultrasound which revealed a solid, isoechoic nodule measuring (1.23 x 1.42 x 2.00 cm) with no calcifications. Fine needle aspiration was consistent with MTC. She denied family history of thyroid cancer. She was advised to stop liraglutide immediately given risk of MTC with GLP-1 receptor agonist use. Preoperative calcitonin and CEA were markedly high at 935 pg/mL and 60.3 ng/mL, respectively. Fortunately, Gallium Ga-68 dotatate PET CT showed no signs of metastatic disease. The patient underwent a total thyroidectomy with bilateral central and lateral neck dissection. No cervical metastases were noted on lymph node dissection. Genetic tumor testing demonstrated a mutation in the RET oncogene (c.3281G>A), which was previously reported as a variant with unknown significance. Screening for hyperparathyroidism and pheochromocytoma was normal. Postoperative calcitonin and CEA were <2.0 pg/mL and 3.2 ng/mL respectively. The patient continues MTC surveillance under the care of a multidisciplinary team. Discussion: Our case is the first case in literature that identifies the RET oncogene (c.3281G>A) mutation as a pathogenic variant associated with MTC. It also emphasizes the need for close monitoring for thyroid nodules in patients on GLP-1 receptor agonists and pre-existing thyroid disease, through a comprehensive physical examination and neck ultrasound if needed. Presentation: 6/2/2024

6504 Cerebellar Metastases from Papillary Thyroid Cancer; An Unusual Presentation

Abstract Disclosure: L.E. Chozet: None. A. Gilbert: None. M.A. Escobar Vasco: None. Background: Differentiated papillary thyroid cancer is known to have a very favorable prognosis. Brain metastases arising from papillary thyroid carcinoma are a very rare complication seen in approximately 1% of all cases of differentiated thyroid cancer with cerebellar metastases being even more uncommon. We present a case of a patient presenting with ataxia as the initial and only symptom of papillary thyroid carcinoma, found to have cerebellar metastases. Clinical Case: A 68-year-old man presented with ataxia for 1 week prior to arrival to hospital. CT head revealed hyperdense lesions in the right frontal lobe and left posterior cerebellar hemisphere. The patient underwent resection of left cerebellar mass with final pathology consistent with metastatic papillary thyroid carcinoma. Tumor cells were positive for TTF-1, thyroglobulin, CAM5.2, CK7, and PAX8, and negative for CK5/6, CK20, inhibin, and Napsin A. Ultrasound of the thyroid revealed multinodular goiter with dominant left thyroid lobe nodule 4 cm in size. PET CT showed left Thyroid mass with direct extension to adjacent lymph nodes, right anterior rib mass, left adrenal metastasis and right frontal lobe and left cerebellar metastasis. He received stereotactic radiosurgery with 5 out of 5 treatments completed. He subsequently underwent total thyroidectomy with left modified radical neck dissection, with pathology showing pT3bN1bM1. Next Generation Sequence positive for V600E, RADS1CR193, TERT PROMOTER -124C>T. After multidisciplinary team discussion, it was determined that the best course of action was to refer the patient to MD Anderson for evaluation, candidacy for prospective therapeutic clinical trials. Conclusion: This case demonstrates how differentiated papillary thyroid cancer, despite its favorable prognosis, can still prove to be a dangerous disease especially if undiagnosed for several years. This case also illustrates how papillary thyroid carcinoma can remain clinically silent for years and first present with atypical symptoms consistent with advanced metastases. Presentation: 6/2/2024

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

12313 Parathyroid Carcinoma Presenting As Right Foot Pain And Swelling In A Young Male - A Case Report

Abstract Disclosure: F.E. Sorsona: None. L. Lopez: None. Parathyroid carcinoma is a rare cause of hyperparathyroidism that is challenging to diagnose. We report a case of parathyroid carcinoma with an unusual initial presentation of right foot pain and swelling in a young 26-year-old Filipino male. Physical examination revealed a palpable 1 x 1 cm mass with tenderness on his right foot. Initial work-up showed a persistently elevated serum ionized calcium (range: 1.7 - 2.19 mmol/L) with markedly high intact parathyroid hormone (1,890 pg/ml). A right foot x-ray revealed a lytic bone lesion on the 3rd metatarsal. Skeletal survey revealed diffuse lytic bone lesions. Comprehensive neck ultrasound showed a 4 x 1.6 x 2.5 cm complex nodule adjacent to the inferior pole of the left lobe of the thyroid gland with intralesional calcifications. A 4D CT scan showed a 3.3 x 2.2 x 2 cm hypervascular nodule inferior to the left thyroid lobe with early contrast washout, likely parathyroid in origin, and a possible brown tumor in the right fourth rib. Patient underwent parathyroidectomy with intraoperative PTH monitoring showing a marked reduction of intact PTH by 87% (235.9 pg/ml from 1,890 pg/ml), accompanied by reduction of serum ionized calcium. The histopathology reported parathyroid carcinoma highlighted by lymphovascular invasion, atypical round cells in sheets and nests, with enlarged, mildly pleomorphic, hyperchromatic nuclei and prominent nucleoli. Two months after surgery, normal serum ionized calcium was maintained with calcium supplementation with reported relief of right foot pain and swelling. The patient continues to follow up regularly for monitoring of treatment response. Presentation: 6/2/2024

8155 Isolated Hypothalamic-Pituitary Langerhans' Cell Histiocytosis in Adult Patients

Abstract Disclosure: A. Vu: None. M. Aguilera: None. J. Shakil: None. R. Al-Ward: None. Introduction: Langerhans cell histiocytosis (LCH) is an infiltrative disease due to clonal proliferation of immature dendritic cells mainly affecting children and seen in adults in less than 30% of cases. It can present as localized or with systemic manifestations, with isolated hypothalamic-pituitary lesions being exceptionally rare. Our report adds to the limited published literature by presenting two cases of isolated hypothalamic-pituitary LCH diagnosed in adults. Furthermore, one of the cases reveals a rare association with papillary thyroid cancer (PTC). Case 1: 35-year-old woman with no past medical history presented with 4 year history of amenorrhea and weight gain and more recently, polyuria and polydipsia. Further investigations showed hypogonadotropic hypogonadism, central hypothyroidism, and mildly elevated prolactin. She couldn’t complete water deprivation test due to extreme thirst. A dedicated pituitary MRI showed marked infundibular enlargement, concerning for hypophysitis. An extensive workup including assessments for autoimmune etiology, sarcoidosis, infections, and low-grade tumors, did not identify a definitive etiology. A PET scan was obtained (to rule out LCH and Erdheim Chester disease), which showed increased uptake in the pituitary stalk. Due to otherwise negative workup, transsphenoidal biopsy of the pituitary lesion was done. Post-procedure, diabetes insipidus (DI) was diagnosed due to elevated sodium while fasting for the procedure. Tissue examination revealed increased histiocytes and lymphocytes, and a positive BRAF V600E mutation confirming LCH as the underlying diagnosis. Case 2: 26-year-old male with history of LCH limited to the skull, in remission for 8 years after chemotherapy, presented with 4-week history of polyuria, polydipsia and weight loss. A 24-hour urine collection resulted in 6.5L of urine. During water deprivation test, there was notable increase in serum sodium, serum osmolarity, and urine osmolarity. Initial pituitary MRI was normal, but subsequent imaging revealed the loss of the posterior pituitary bright spot. PET scan showed focal FDG avidity in the right lower thyroid lobe, confirmed on fine needle aspiration as PTC with BRAF mutation. He underwent total thyroidectomy and is currently receiving chemotherapy for LCH recurrence. Discussion: LCH is infrequent in adults, presenting with variable manifestations based on affected organs. In the multifocal form, the hypothalamic-pituitary axis is involved in 5-50% of cases. Our report describes two unique cases with only four other reported cases of isolated hypothalamic-pituitary axis LCH in adults. Central diabetes insipidus can be seen before the diagnosis or as the disease progresses. Pituitary biopsy, although invasive, should be considered when the diagnosis is not clear. The association of PTC with a BRAF mutation is extremely rare and has been reported. Presentation: 6/2/2024

12350 A Rare Case Of Giant Parathyroid Adenoma Managed Medically For 8 Months: A Case Report

Abstract Disclosure: S. Labram: None. L. Bilandzic: None. Background: Single parathyroid adenoma is the most common cause of primary hyperparathyroidism, and is attributed to approximately 85% of cases[1]. However, those classified as giant (weighing over 3.5 g and having a size greater than 2cm2) are exceedingly rare. This reports a rare case of primary hyperparathyroidism caused by giant parathyroid adenoma and details biochemical response following medical and surgical management. Case Report: A 64 year old black female presented with severe abdominal pain, confusion and constipation. Investigations revealed severe hypercalcemia of 17.3 mg/dl with massively elevated parathyroid hormone of 1255 pg/mL. Ultrasound showed a large hypoechogenic lobulated mass inferior to the left thyroid lobe representing a giant parathyroid adenoma. Due to delayed surgery the patient was initially treated medically over the course of 8 months. Over these months she was admitted to hospital 3 times for symptomatic hypercalcemia and received a total of 3 zolendronic acid infusions. Despite this she was unable to achieve long term remission of hypercalcemia. Cinacalcet was added and tolerated at the dose of 30 mg daily. Hypercalcemia improved, but remained elevated at a range of 11-13 mg/dL and the symptoms of brain fog and constipation did not subside entirely. She was eventually able to undergo surgical resection, and a giant parathyroid adenoma weighing 8.9 g was excised. Intraoperative intact parathyroid hormone (IOiPTH) sampling showed > 50% reduction (prior to removal 878pg/mL, 10 minutes after removal 132 pg/ml, 20 minutes after removal 96pg/mL). Pathological review showed an atypical parathyroid tumor. As the tumor lacked invasive growth it did not meet criteria for carcinoma. Conclusions: This is a rare case of primary hyperparathyroidism caused by a giant solitary parathyroid adenoma. The gold standard for management of primary hyperparathyroidism secondary to parathyroid adenoma is minimally invasive parathyroidectomy. However in our case, due to inability to access immediate surgery, challenging and prolonged medical treatment of severe hypercalcemia followed for 8 months. Ultimately, normalization of calcium level was achieved only by surgical intervention. IOiPTH measurements showed appropriate decrease confirmatory for the complete removal of the adenoma.

8063 Cystic Parathyroid Adenoma: A Rare Cause Of Severe Hypercalcemia

Abstract Disclosure: M. Owrangi: None. F. Hasan: None. Introduction: Parathyroid adenomas are the most common cause of primary hyperparathyroidism, but within this category, a rare subtype exists - cystic parathyroid adenomas (CPAs). Comprising only 0.5-1% of all parathyroid lesions, CPAs present unique diagnostic and therapeutic challenges. We report a case of a female patient presenting with severe hypercalcemia caused by a CPA. Case presentation: A 44-year-old African American female with a history of nephrolithiasis presented with abdominal pain and signs of dehydration. Labs were remarkable for serum calcium 13.2 mg/dL, albumin 4.0 g/dL, phosphorus 1.8 mg/dL, iPTH 617.7 pg/mL, 25-OH vit D 12.1 ng/mL, creatinine 0.85 mg/dL. She was initially resuscitated aggressively with IV fluids resulting in an improvement in serum calcium level to 10.3 mg/dL. Thyroid US showed a cystic nodule deep to the left thyroid lobe. Sestamibi parathyroid scan was consistent with a left superior parathyroid adenoma. She underwent 2 gland parathyroidectomy 3 months after the initial presentation. Intraoperatively serum PTH decreased by 91% after resection of the 2 parathyroid adenomas. Pathology confirmed the presence of 2 parathyroid adenomas, the larger one measuring 2.8 cm and weighing 3.8 g. Discussion: We describe a case of a middle-aged female presenting with severe hypercalcemia due to CPA. Her initial presentation was concerning for parathyroid carcinoma given the severity of hypercalcemia. However, the radiologic findings, coupled with surgical pathology, indicated that she had CPA. CPAs can be either functional, causing primary hyperparathyroidism (PHPT) with elevated serum calcium levels, or non-functional, remaining asymptomatic. Clinical features of PHPT associated with CPAs are similar to those with solid adenomas and include fatigue, GI symptoms, nephrolithiasis, bone pain, and neuropsychiatric manifestations. However, CPAs may exhibit certain distinct presentations: i) higher pre-operative serum calcium levels; and ii) increased risk of symptomatic hypercalcemia. Despite their rarity, CPAs deserve special attention due to their unique presentation, challenging diagnosis, and potential for severe hypercalcemia. Surgical parathyroidectomy is the definitive treatment for functional CPAs. Accurate localization and complete excision of the adenoma are crucial to avoid recurrence. Most CPAs occur in the fourth and fifth decade of life and are more common in women (female to male ratio of 2.5:1). 65-85% of cases are located in the neck and the majority arise from the inferior parathyroid glands and are left-sided, and may very rarely be intrathyroidal. Presentation: 6/2/2024

7191 When Pain Is Misdiagnosed: A Case of Parathyroid Carcinoma Masked as Fibromyalgia

Abstract Disclosure: H. Pham: None. P.V. Kumar: None. S. Taylor: None. Parathyroid carcinoma is a rare and aggressive cause of hyperparathyroidism, typically associated with <1% of primary hyperparathyroidism cases. Incidence occurs mainly in the 5th decade of life, with less than 4% of all cases presenting in patients under age 30. Here, we highlight a case involving a 28-year-old woman with fibromyalgia who presented for worsening right shoulder pain in the setting of progressive, poorly characterized pain for the past year. Her initial physical exam was unremarkable aside from a non-tender left sided neck enlargement. However, her laboratory results were significant for corrected serum calcium of 15 mg/dL, serum phosphorus of 2.3 mg/dL, parathyroid hormone (PTH) >2500 pg/mL, and alkaline phosphatase 1604 units/L. X-ray of her right shoulder demonstrated mottled bone concerning for degenerative disease. Thyroid ultrasound revealed a complex cystic lesion posterior to the left thyroid lobe measuring 5.3 x 3.9 x 2.9 cm, worrisome for giant parathyroid adenoma. CT abdomen/pelvis showed diffuse osteosclerosis and innumerable lytic lesions, consistent with osteitis fibrosa cystica, as well as bilateral nephrolithiasis, likely medullary nephrocalcinosis. Her hypercalcemia was treated with aggressive hydration with normal saline and IV pamidronate. She underwent surgical resection of her parathyroid adenoma, which was unfortunately complicated by symptomatic hypocalcemia requiring prolonged care in the ICU. Her calcium levels did improve within a few days, and she was subsequently discharged with close outpatient follow-up. Final pathology report showed predominant thickened trabecular growth pattern with focal vascular invasion consistent with parathyroid carcinoma. Our patient’s case represents a rare presentation of parathyroid carcinoma in a young patient without any additional risk factors. Although atypical, her severe symptomatic hypercalcemia, nephrolithiasis, presence of large neck mass, and diffuse skeletal disease warranted immediate concern for malignant hyperparathyroidism instead of benign adenoma. Delayed diagnosis in our patient led to prolonged bone disease and severe complications. While hungry bone syndrome typically manifests post-parathyroidectomy in patients with end-stage renal disease, our patient experienced this complication in the setting of advanced, untreated hyperparathyroidism. We should consider hypercalcemia and hyperparathyroidism in our differential diagnosis for chronic pain, especially if pain remains uncontrolled with conservative measures. The most appropriate initial test for evaluation of hypercalcemia is a PTH level to distinguish between PTH-dependent and PTH-independent etiologies. Parathyroid carcinoma, even in young patients, should be considered when PTH is >3x upper limit of normal, serum calcium is >14, or skeletal and renal involvement is present. Presentation: 6/3/2024

8409 Thyroid Nodules A to V: A Discussion on Thyroid Nodules and a Case Report of a Rare Thyroid Arteriovenous Malformation

Abstract Disclosure: M. Townsend: None. M. Brennan: None. C. Kazmierczak: None. P. Czako: None. Introduction: Thyroid nodules are an increasingly common finding on imaging, and the differential is broad. Arteriovenous malformations (AVMs) are a very rare cause of thyroid lesions, with only 6 reported cases to date. Given their scarcity, there is a lack of information regarding these lesions and how they are diagnosed and managed. Our case aims to address these gaps in information. Case: A 58-yo female with a history of hypertension was found by her PCP to have an enlarged left thyroid lobe with a new left sided bruit and palpable thrill. She had undergone prior thyroid ultrasonography for the enlarged left thyroid lobe which noted dilated and tortuous vascular structures at the posterior aspect of the left thyroid consistent with varices. These were being monitored clinically. Thyroid function tests were all normal. Due to concern for atherosclerotic disease, carotid ultrasound was obtained and showed patent carotid arteries with a large left sided thyroid mass. CTA of the neck revealed the mass to be a large (6.0 x 3.0 x 2.4 cm) AVM centered at the left thyroid gland. She underwent diagnostic angiography that confirmed the size of the mass and showed predominant arterial supply from the left superior thyroidal artery as well as bilateral inferior thyroidal arteries. Since the patient was asymptomatic with no reported neck pain, dysphagia or dyspnea, non-operative management with angioembolization was pursued given the risk of significant blood loss with surgical intervention. Following angioembolization, the results and adequacy of treatment are to be followed with repeat imaging given the high risk of reoccurrence. Discussion: AVMs of the thyroid are a very rare but clinically significant cause of thyroid lesions. Left untreated, they can grow in size and lead to compression of the esophagus or trachea, serious bleeding and high output heart failure. Their presentation is often non-specific and on routine thyroid imaging they can be difficult to differentiate from malignant tumors or varices, as in the case of our patient. Management prioritizes embolization, either alone or in conjunction with surgery, depending on the clinical scenario. Regardless of the treatment modality, reoccurrence rates remain high. Conclusion: Our case aims to add to the available information about thyroid AVMs and discuss the clinical presentation, challenges in diagnosis, imaging findings and treatment modalities available to manage these lesions. Presentation: 6/2/2024

7357 Microscopic Papillary Thyroid Cancer Presenting with Cranial Nerve Palsies due to Metastatic Cervical Lymphadenopathy: A Case Report

Abstract Disclosure: N.N. Mukhtar: None. C. Zuo: None. B.R. Haugen: None. Introduction: Tumors metastasizing to head and neck are considered a rare cause of cranial nerve palsy (CNP). In this report, we describe an unusual presentation of metastatic microscopic follicular variant papillary thyroid cancer (FVPTC) presenting with CNP. Case Summary: A 68-year-old previously healthy female presented to her primary care physician with a 6-week history of difficulty speaking and chewing food. She did not notice any dysphagia, change in voice or shortness of breath. Cranial nerve examination was evident for palatal asymmetry, left-sided uvular and right-sided tongue deviations suggesting right glossopharyngeal and hypoglossal nerve palsies. Neck examination revealed a normal thyroid gland without palpable nodules however, the patient had multiple enlarged painless right cervical lymph nodes (CLN). MRI of the brain was normal. CT of the neck and chest showed enlarged, calcified right level II and III CLN (largest 4x3.5 cm) compressing the right internal jugular vein. In addition, bilateral pulmonary nodules (largest 1.7x1.5 cm) suspicious for metastasis were seen. CT-guided biopsy of left upper lobe lung nodule was consistent with metastatic thyroid cancer (positive PAX-8 and TTF-1 immunostaining). Neck ultrasound did not show any thyroid nodules, but did confirm 4 enlarged right CLN (largest 2.9 cm). The patient was referred to our multidisciplinary clinic for further evaluation. Based on the duration of her symptoms (6 weeks), her CNP was most-likely irreversible and agreement to proceed with total thyroidectomy, central and right lateral neck dissection aiming for complete resection in preparation for future treatment with radioactive iodine. Preoperative thyroglobulin level was 30.7 ng/ml (1.6-50), thyroglobulin antibody 24 U/mL (<40) and TSH 0.6 mIU/L (0.4-4.6). Intra-operatively; the patient had extensive, bulky lymphadenopathy extending to surrounding neck muscles and completely encasing right jugular vein. Histopathological examination of the resected tissue showed a unifocal right thyroid lobe microscopic (6x4x3 mm) infiltrative follicular variant papillary thyroid cancer (FVPTC). No extrathyroidal extension, necrosis, angioinvasion or lymphatic invasion were identified. Mitotic index was 3/ 2mm2. 13 out of 36 lymph nodes were positive for metastatic thyroid cancer (3/3 level II, 2/17 level III, 8/16 level IV), largest was 4.6 cm with extra-nodal extension. The patient was discharged on suppressive dose levothyroxine. Molecular studies: Next generation sequencing of the lung biopsy was negative for BRAFV[6]00E mutation and further molecular analyses are ongoing. Conclusion: This case describes two unique presentations of thyroid cancer; a microscopic FVPTC associated with large lateral cervical lymph node metastasis and, CNP as the initial presentation of thyroid cancer which to our knowledge, has not been reported previously. Presentation: 6/2/2024

8161 A Rare Case of Malignant Melanoma Metastatic to the Thyroid Gland

Abstract Disclosure: J. Ferri-Guerra: None. O. Abdulhussein: None. E. Kasper-Guerra: None. G. Madrigal Loria: None. L. El Hage: None. 69 yo female presented with neck swelling in 2014. TSH was normal. Thyroid ultrasound showed multiple nodules with a right 2.9 x 2.3 x 2.1 cm that was cold on subsequent thyroid uptake scan. FNA of the right nodule in 08/2014 showed malignant cells with spindle cell pattern thought to be medullary thyroid cancer. She was scheduled for total thyroidectomy but presented with small bowl obstruction prior to her surgery and was diagnosed with metastatic melanoma (BRAF +). Initial PET scan showed a 4.1 x 2.8 x 2.8 cm hypermetabolic right thyroid lobe lesion in addition to other multiple hypermetabolic lesions consistent with known melanoma. The thyroid FNA specimen correlated with the small bowel excision specimen and showed similar features diagnosing metastatic melanoma to the thyroid gland.She was started on ipilimumab with subsequent scan in 04/2015 showing increase in right thyroid mass size to 5.4 x 4.2 x 9 cm with mixed results of other metastatic locations. She was switched to pembrolizumab and later dobrafenib/trametinib in 05/2015. Imaging thereafter showing significant improvement including a decrease in the right thyroid nodule size to 1.6 cm x 2.5 cm x 2.4 cm with no hypermetabolic activity on further PET scans. Repeat thyroid ultrasound in 2021 showed multiple nodules with a 2.2 x 1.5 x 1 cm nodule in the right. Repeat FNA of the right nodule was benign. Last imaging in 2023 showed stable nodules. Conclusion: metastasis to thyroid gland from malignant melanoma is a rare finding and should be considered in rapidly growing thyroid nodules. These lesions can be treated with targeted therapy that can spare affected individuals surgery. Presentation: 6/1/2024

7008 Challenges in the Management of Thyroid Lymphoma - Case Report

Abstract Disclosure: F. Toloza Bonilla: None. P. Veeraraghavan: None. R. Lakhotia: None. M. Roschewski: None. N. Nilubol: None. S. Gubbi: None. J. Klubo-Gwiezdzinska: None. Introduction: Primary thyroid lymphoma is an extremely rare thyroid malignancy accounting for less than 5% thyroid malignancies. The management depends on the histological subtype and tumor staging, typically involving chemotherapy alone or combined with radiotherapy. Although, surgical intervention is generally not recommended, given the potential surgical risks and the absence of additional benefits compared to chemoradiation therapy, it is reserved to obtain tissue diagnosis and to treat compressive symptoms. Clinical Case: A 66-year-old Caucasian female presented with dysphagia to solid food and acute neck swelling for a few weeks. History was negative for fever, weight loss or nocturnal diaphoresis. The patient had a history of primary hypertension, pre-diabetes, and Hashimoto’s hypothyroidism. A neck computed tomography (CT) scan showed a thyromegaly (8.3 x 5.8 cm) and bilateral cervical lymphadenopathy. Thyroid ultrasound showed sub centimeter nodules in the right mid-gland and a heterogeneous and irregular left thyroid lobe. TSH was normal (0.87 mcIU/mL [0.27-4.2]). She was treated for suspected subacute thyroiditis with prednisone for two weeks, showing initial clinical improvement, but symptoms recurred after steroids were stopped. Subsequently, a CT neck and fludeoxyglucose F18 (FDG) positron emission tomography (PET) scan demonstrated FDG avid thyroid enlargement with local adenopathy and rightward tracheal deviation. Lymph node, FNA, core biopsies and molecular testing were consistent with stage IIE MYC/BCL6 rearranged diffuse large B-cell lymphoma as she had no bone marrow or central nervous system (CNS) involvement. The patient’s treatments included four cycles of etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin, and rituximab with ibrutinib added after the first cycle and intrathecal methotrexate with cycles 3-6, to reduce the risk of CNS involvement. A 6-month post-therapy follow-up showed complete response (CR) on imaging with symptoms resolution. Four months later, she experienced worsening symptoms, including dysphagia with solids and liquids, and hoarseness despite CR to therapy and stable CT imaging. Laryngoscopic evaluation noted left vocal cord paralysis and extrinsic compression of the tracheoesophageal groove. Patient opted for a left hemithyroidectomy, experiencing excellent symptom relief. Surgical pathology showed findings consistent with a necrotic tumor and residual areas of lymphocytic thyroiditis. No active DLBCL was appreciated. The patient remains in remission and continues to be symptoms-free 24 months post-thyroid lymphoma treatment. Conclusion: While thyroidectomy is not typically recommended as the initial treatment for primary thyroid lymphoma, it emerges as a potentially effective option to manage recurrent or persistent compression symptoms following the completion of medical therapy. Presentation: 6/3/2024

7817 A Rare Case of Intrathyroidal Thyroglossal Duct Cyst Presenting as a Rapidly Expanding Left Thyroid Goiter

Abstract Disclosure: C.M. Godar: None. A.J. Spiro: None. K.F. Brown: None. M.K. Shakir: None. T.D. Hoang: None. Introduction: Thyroglossal duct cysts are the most common congenital cyst in the head and neck, found during childhood as a midline neck mass. We present a rare case of a large intrathyroidal thyroglossal duct cyst with left lateral extension in an adult patient. Case Report: A 50-year-old man with family history of familial adenomatous polyposis presented for thyroid nodule evaluation. Thyroid ultrasound for screening of thyroid cancer showed a 4.8 x 4.5 x 2.5cm mixed cystic/solid hyperechoic thyroid nodule with smooth margins in the left lower thyroid lobe. He reported no compressive symptoms. FNA with standard 27G needle was insufficient for evaluation with Bethesda I result. Attempted syringe aspiration did not produce cystic fluid for analysis. The patient returned to clinic 8 weeks later due to visible enlargement of his anterior neck and new neck pressure with swallowing. Physical exam was significant for a new, firm palpable mass over the left thyroid isthmus. Bedside ultrasound noted expansion of the previously visualized mass now extending into the thyroid isthmus. FNA was reattempted with a 25G needle, and cytologic material was again inadequate. He elected to undergo left hemithyroidectomy. Histologic sections demonstrated a 3.4cm simple squamous, non-keratinizing cyst lining overlying a thickened fibrotic wall with mixed acute and chronic inflammation surrounded by benign thyroid tissue, consistent with an intrathyroidal thyroglossal duct cyst. Discussion: The thyroglossal duct derives from epithelial tissue during embryogenesis and atrophies during weeks 8-10 of gestation. A persistent duct may lead to cyst formation in the presence of remnant epithelial tissue secretions and local neck inflammation. A thyroglossal duct cyst is usually located midline in the anterior neck. This stands in comparison to a branchial cleft cyst, which arises due to failure of atrophy of the second branchial groove during embryogenesis and forms a cyst that is usually located in the upper lateral neck compartment. Other common neck masses include lipomas, dermoid cysts, or ectopic thyroid tissue. This case highlights the rarity of intrathyroidal thyroglossal duct cyst in an adult patient and the importance of definitive diagnosis and appropriate management. Presentation: 6/2/2024

7200 A Unique Case Of Hypercalcemia From Primary Hyperparathyroidism With Thymoma And Concurrent Pulmonary Tuberculosis

Abstract Disclosure: S. Jing Hang Randy: None. L. Huiling: None. Background: Several case reports have reported the rare association of thymoma with primary hyperparathyroidism. We describe a unique case of hypercalcemia with such association but was also found to have concurrent pulmonary tuberculosis. Clinical Case: A 50-year-old Indian female with a significant history of anterior mediastinal mass underwent median sternotomy with mass resection and was found to have peri-operative hypercalcemia. Her only complaint was chronic cough. Initial investigations showed high adjusted calcium 2.78 mmol/L (2.15– 2.50 mmol/L), normal phosphate 1.1 mmol/L (0.8– 1.4 mmol/L) and high PTH 24.7 pmol/L (1.6– 6.9 pmol/L). Apart from the mediastinal mass, a whole-body CT scan showed multiple prominent mediastinal lymph nodes with non-specific subcentimetre lung nodules. The post-operative finding was a Type AB thymoma with necrotizing granulomatous inflammation in adjacent station I lymph node. Differentials for patient’s hypercalcemia included primary hyperparathyroidism, malignancies such as lymphomas and infectious causes in particular tuberculosis. Her 25-OH Vitamin D was low at 9 ug/L (30 - 100 ug/L), 1,25-dihydroxyvitamin D was elevated at 205 pg/mL (18-64 pg/mL) while creatinine, ALP, serum ACE and PTHrP were unremarkable. She was subsequently admitted for worsening hypercalcemia, fever and left pleural effusion with generalized lymphadenopathy where she underwent an Endobronchial Ultrasound-guided Transbronchial Needle Aspirate of station IV lymph nodes before being started on tuberculosis treatment. The AFB culture showed Mycobacterium Tuberculosis Complex thereafter. Parathyroid sonography revealed a 2.2cm x 0.9cm x 0.8cm lobulated hypoechoic lesion posterior to the inferior pole of left thyroid lobe. However, a confirmatory sestamibi scan could only be done 6 weeks post-thymectomy given the raw surgical bed, with a possibility of false-negative result for cervical parathyroid adenoma given a recent thymectomy. It subsequently showed a hyperfunctioning left inferior parathyroid nodule with no other suspicious focal uptake in the neck or mediastinum. Patient underwent a focused left parathyroidectomy. Histology showed features consistent with parathyroid adenoma. A stepwise trajectory of her calcium normalization was observed with hydration, intravenous zoledronic acid for her osteoporosis, tuberculosis treatment, adjuvant radiation therapy for her thymoma with margins involvement, and parathyroidectomy. Conclusion: This case illustrates the challenges faced while considering localizing scans for primary hyperparathyroidism with recent thymectomy given the common embryological origin of inferior parathyroid and thymus. It also demonstrates the possible co-existence of separate pathologies in hypercalcemia and the need to exercise prudent clinical judgement to further evaluate for these various etiologies. Presentation: 6/2/2024