Mucin-producing papillary thyroidal carcinoma with unusual histology: A rare case report

Background: Although mucinous carcinoma or mucoepidermoid carcinoma of the thyroid gland are an extremely rare but an established entity, papillary thyroidal carcinoma (PTC) with mucin production is also exceedingly rare. Case report: We reported one rare case of mucin producing PTC with unusual histology. The patient was 71 years-old Japanese man. The hemi-thyroidectomy was performed. Histologically, the tumor cells harbored the similar features with conventional PTC, but this case indicated extracellular and intracellular mucin. On the other hand, the tumor showed cystic-papillary or cribriform growth of the columnar tumor cells. Conclusions: We diagnosed it as mucin-producing PTC with columnar cell variant (CCV). We examined it immunohistochemically, and this case expressed TTF-1, thyroglobulin, and cytokeratin (CK)7, but was negative for HBME-1. We discuss on the differential diagnosis.