MON-350 The Secret in Their Orphan Annie Eyes: A Case of Sclerosing Mucoepidermoid Carcinoma with Eosinophilia Appearing As Papillary Thyroid Carcinoma

Abstract Disclosure: H. Tranton Junior: None. S. Eng: None. J.A. Vu: None. Sclerosing mucoepidermoid carcinoma with eosinophilia of the thyroid gland is an incredibly uncommon oncologic pathology that is typically analogous to salivary gland mucoepidermoid carcinoma. The rarity of this condition is such that even with multidisciplinary efforts, dramatic interventions are typically performed to best ensure patient safety. This case concerns a 66-year-old woman with no previous family history of thyroid cancer. Patient was found to have a left-sided thyroid nodule on ultrasound. Initial ultrasound remarkable for 3.1 cm TR x 2.4 cm AP x 4.5 cm CC nodule with ACR TI-RADS score of 4. Recommendation at the time was follow-up ultrasound in one year for further evaluation, without fine needle aspiration. Repeat ultrasound of the left-sided nodule showed significant change in size by at least 3 mm in 2 planes, measuring 3.8 cm TR x 2.8 cm AP x 3.8 cm CC, and fine needle aspiration was performed. At time of follow-up, the patient reported having some associated symptoms of mild vocal changes with intermittent hoarseness while speaking as well as occasional dysphagia. Initial pathology of fine needle aspiration was suggestive of possible papillary thyroid carcinoma. Left lobectomy was performed, and the surgical pathological specimen was more remarkable for sclerosing mucoepidermoid carcinoma with eosinophilia and not analogous to its salivary gland counterpart in terms of specific molecular arrangement. Case was brought to a multi-disciplinary board of head/neck surgeons, radiation oncologists, medical oncologists, radiologists, nuclear medicine, and pathologists. Due to the rarity of this condition, variable prognosis, lack of grading system for this tumor type, and lack of historical data in terms of ascertaining factors that lead to aggressive disease; complete surgical excision was recommended. Following surgical excision patient was determined to be cancer free. Presentation: Monday, July 14, 2025