A Case of Hyalinizing Trabecular Tumor That Was Difficult to Differentiate from Papillary Thyroid Carcinoma by Fine Needle Aspiration Cytology

Abstract

Hyalinizing trabecular tumor (HTT) is a rare thyroid tumor, and differentiation of this tumor from papillary thyroid carcinoma by fine needle aspiration (FNA) cytology is often difficult. We report a case of HTT in a 45-year-old female patient. FNA cytology revealed evidence of malignancy and we performed total thyroidectomy under the suspicion of papillary thyroid carcinoma (PTC). Histopathology of the thyroidectomy specimen showed features of HTT. HTT is considered as being a benign tumor of follicular cell origin showing a trabecular growth pattern and hyalinized stroma. HTT contains thyrocytes with numerous intranuclear pseudoinclusions similar to PTC, and the possibility of a false-positive result of FNA cytology needs to be considered.