Hsieh Min-Huang, Lin Min-Chieh, Shun Chia-Tung, Chang Tien-Chun
Department of Internal Medicine, China Medical University Hospital, Taichung, Taipei, Taiwan.
Acta Cytol. 2008 May-Jun;52(3):361-5. doi: 10.1159/000325524.
Mixed medullary-follicular thyroid carcinoma (MMFTC) is a rare tumor that has been regarded as a clinicopathologic variant of medullary thyroid carcinoma. MMFTC represents a diagnostic challenge by fine needle aspiration cytology (FNAC).
A 77-year-old woman had a palpable mass on the left side of the neck. It was diagnosed as follicular neoplasm by FNAC; she underwent total thyroidectomy. Pathology revealed follicular carcinoma. Radioactive iodine was administered. An enlarging mass was present in the left mandible later. FNAC showed suspicious follicular neoplasm with predominance of oncocytic cells. Pathology revealed follicular carcinoma with parafollicular cell differentiation. Immunohistochemical analysis demonstrated positive status for thyroglobulin and calcitonin. Simultaneous expression of thyroglobulin and calcitonin within the same neoplastic cell was considered. She underwent several courses of radioactive iodine therapy without significant effect. Interestingly, her serum calcitonin level was not elevated.
Coexpression of thyroglobulin and calcitonin in the same cell is very rare. The component of medullary carcinoma should be considered when encountering an atypical thyroid carcinoma with predominance of cells showing oncocytic changes on FNAC and with clinically poor response to conventional treatment. Immunohistochemistry and pathologic analyses are helpful to confirm the diagnosis, especially in the absence of elevated serum calcitonin level.
混合性髓样-滤泡性甲状腺癌（MMFTC）是一种罕见肿瘤，一直被视为甲状腺髓样癌的一种临床病理变体。MMFTC通过细针穿刺抽吸活检（FNAC）进行诊断具有挑战性。
一名77岁女性颈部左侧可触及肿块。FNAC诊断为滤泡性肿瘤；她接受了全甲状腺切除术。病理显示为滤泡癌。给予放射性碘治疗。后来左侧下颌骨出现肿块增大。FNAC显示可疑滤泡性肿瘤，以嗜酸性细胞为主。病理显示为具有滤泡旁细胞分化的滤泡癌。免疫组化分析显示甲状腺球蛋白和降钙素呈阳性。考虑到同一肿瘤细胞内同时表达甲状腺球蛋白和降钙素。她接受了几个疗程的放射性碘治疗，但效果不明显。有趣的是，她的血清降钙素水平未升高。
甲状腺球蛋白和降钙素在同一细胞中共表达非常罕见。当遇到FNAC显示以嗜酸性细胞改变为主的非典型甲状腺癌且对传统治疗临床反应不佳时，应考虑髓样癌成分。免疫组化和病理分析有助于确诊，尤其是在血清降钙素水平未升高的情况下。
