Thyroid sclerosing mucoepidermoid carcinoma with eosinophilia in conjunction with parotid basal cell adenoma: Cytologic, histologic, and molecular features

Abstract Sclerosing mucoepidermoid carcinoma with eosinophilia (SMECE) is a rare malignancy in the thyroid: only 56 cases with histologic descriptions are reported in the literature and fewer reports describe the cytomorphology. Given the rarity of SMECE, data on the cytomorphologic and molecular features are limited. We report a case of a 53‐year‐old woman with a 5 cm left thyroid mass. Fine‐needle aspiration (FNA) revealed atypia of undetermined significance and pathology of left thyroid lobectomy specimen showed SMECE. Additionally, a left pre‐auricular lump was noted and FNA followed by left superficial parotidectomy showed basal cell adenoma. Next‐generation sequencing showed point mutations in NTRK3 and NF1 . Unlike salivary gland mucoepidermoid carcinoma, MAML2 translocations are not present in SMECE. Even though it is a rare entity, awareness of SMECE of the thyroid is important. In this case report we review the cytomorphologic, histologic, and molecular features.