Hyalinizing Trabecular Tumor of the Thyroid Gland, a Diagnostic Challenge in Fine-Needle Aspiration Cytology: Case Report.

Hyalinizing trabecular tumor (HTT) is a rare thyroid tumor with low to minimal malignant potential. HTT is often misinterpreted as other thyroid tumors, including papillary thyroid carcinoma (PTC) and medullary thyroid carcinoma (MTC), on fine-needle aspiration (FNA) cytology, because of its overlapping cytologic features, such as nuclear grooves and intranulcear pseudoinclusions. Although cytopathologists cannot definitely conclude HTT by FNA cytology, suspicion of HTT is necessary to avoid misdiagnosing HTT as PTC or MTC and to avoid unnecessary aggressive treatment. Here, we report a case of HTT with novel cytologic features in CellPrep liquid based cytology that was diagnosed as suspicious for papillary carcinoma by FNA and finally diagnosed as HTT in the surgical specimen.