SAT550 Warthin-like Variant of Papillary Thyroid Carcinoma: An Even Rarer Presentation

Abstract

Abstract Disclosure: J. Kunadia: None. S. Chablani: None. Introduction: We present a rare case of Warthin-like variant of papillary thyroid carcinoma (WLPTC) with later development of a second primary malignancy. Clinical Case: A 56 year old female with hypertension, hyperlipidemia, ulcerative colitis, asthma, and a strong family history of cancer presented in 2017 for evaluation of an enlarged thyroid gland noted by her primary care provider. Patient was asymptomatic and denied prior thyroid disease and head or neck radiation. Labs demonstrated normal TSH and free T4 levels. TPO antibodies were elevated to 1,155 IU/mL (reference range 0.0 – 5.5 IU/mL). Thyroid US was notable for a diffusely enlarged thyroid gland containing a 1.4 x 0.6 x 1.0 cm solid, hypoechoic nodule without calcifications in the upper pole of the right lobe. Shared decision-making resulted in a plan for continued surveillance. Repeat thyroid US in 2018 demonstrated that this nodule had increased in volume by 56.25%, now measuring 1.4 x 0.75 x 1.25 cm. Fine needle aspiration (FNA) biopsy was performed and positive for papillary thyroid carcinoma (PTC). Patient underwent total thyroidectomy; pathology revealed a 1.2 x 1 x 0.9 cm WLPTC and 0.2 cm papillary thyroid microcarcinoma. There was no evidence of extrathyroidal extension, angioinvasion, or lymph node involvement. Follow-up neck US in 2020 demonstrated a 0.4 cm hypoechoic ovoid structure in the left thyroid bed and an enlarged but morphologically normal-appearing right level II lymph node. Repeat neck US in 2021 showed the appearance of a new 2.8 cm right level II lymph node; FNA was positive for malignancy with negative thyroid transcription factor-1 staining and undetectable thyroglobulin. Patient underwent an excision biopsy of the lymph node, and pathology was consistent with metastatic adenoid cystic carcinoma (ACC). A right submandibular gland lesion detected on subsequent MRI head and neck was resected and confirmed to be the primary source of ACC. Patient was treated with adjuvant radiation therapy with adequate response to therapy. Conclusion: WLPTC is a rare subtype of PTC that accounts for 0.2-1.9% of cases and carries a strong association with Hashimoto’s thyroiditis. It is histologically characterized by papillary architecture, oncocytic changes, nuclear features of PTC, and dense lymphoplasmacytic infiltration of the papillary cores. WLPTC is considered to have a favorable prognosis given its low frequency of lymphovascular invasion and low recurrence risk. This case also highlights the importance of keeping a broad differential when evaluating new findings on neck US in patients with a history of thyroid cancer. Metastases to cervical lymph nodes most commonly occur from head and neck tumors. However, to date, only one other case of PTC with second primary malignancy of salivary ACC has been reported. Presentation Date: Saturday, June 17, 2023