Immature thyroid teratoma with predominant neuroepithelial component: fine needle aspiration cytology findings

Abstract

A primary thyroid teratoma is uncommon, the disease being more prevalent in infants. In adults, the tumour is even less common with less than 40 cases documented in the English literature. The neoplasm is usually malignant in such a setting in contrast to the usual benign tumour in infancy. In this report, we describe the cytological findings of an immature teratoma affecting the thyroid gland of a 33-year-old Chinese woman who presented with a right sided thyroid lump for 4 months. The fine needle aspiration material disclosed single and clusters of medium-sized, primitive appearing cells with stippled chromatin. In addition, there were rosettes identified, suggesting neuroepithelial differentiation. The excised specimen revealed immature teratoma (encapsulated follicular tumour with immature teratoma) with primitive neuroectodermal, mesodermal and endodermal tissue derivatives. The neuroectodermal component corresponded to the tumour cells identified on the cytology sample. As the description of this thyroid neoplasm on cytology is very rare, this report serves to increase awareness of this entity. A summary of the reported cases of immature (malignant) thyroid teratoma as well as the cytological and histological features are presented. The problems in diagnosing this neoplasm on cytology are also highlighted.