Paraganglioma-like medullary thyroid carcinoma: A case report and literature review.

Medullary thyroid carcinoma (MTC) accounts for 3%-5% of all thyroid malignancies. Most MTC can be diagnosed by their typical cytologic and histologic morphology and immunohistochemical features. However, some rare variants of MTC may pose diagnostic difficulties on both cytology and histology. Paraganglioma-like MTC (PLMTC) is a rare, but widely recognized variant of MTC. PLMTC is known to share morphological and architectural similarities with paraganglioma, hyalinizing trabecular tumor, and carcinomas of thyroid follicular cell origin, such as follicular carcinoma and follicular variant of papillary thyroid carcinoma. The combination of clinicopathologic features and a battery of immunohistochemical markers is essential for making a correct diagnosis. Herein, we report one case of PLMTC with both cytologic and histologic features and review the clinicopathologic features of previously reported cases.