Cytological Features of a Lymphoepithelial Cyst Collected from Fine Needle Aspiration of the Thyroid Gland That Mimicked Papillary Thyroid Carcinoma: A Case Report

ABSTRACT

Since its first description in 1989, lymphoepithelial cyst of the thyroid gland (LEC-T) has been generally considered a branchial cleft derivative similar to its presentation in other sites, including thymus, parathyroid, and pancreas. However, its characterization has mainly focused on histologic and sonographic findings, and cytological findings are generally described simply or left out entirely. Fine needle aspiration cytology (FNAC) of our case showed large tissue fragments of epithelial cells on a background of lymphocytes. Some areas showed sheets or small nests of squamoid cells, which were closely admixed with clusters of lymphoid cells. Squamous cells contained relatively moderate to large amounts of eosinophilic cytoplasm and vesicular nuclei with occasional nuclear grooves that lacked intranuclear inclusions. Some cells demonstrated keratinization and nuclear atypia. Herein, we describe FNAC findings of LEC-T and review other possible diagnoses.