Yamada Makoto, Sezaki Shota, Ikeya Tomonari, Furuta Masatoshi, Mizuno Shogo, Otsuki Yoshiro
Department of Clinical Laboratory, Seirei Hamamatsu General Hospital, Hamamatsu, Japan.
Department of Pathology, Seirei Hamamatsu General Hospital, Hamamatsu, Japan.
Diagn Cytopathol. 2025 Nov;53(11):E221-E226. doi: 10.1002/dc.70011. Epub 2025 Aug 23.
Intrathyroidal thymic carcinoma (ITTC) is a rare malignant thyroid tumor that is similar to thymus epithelium-related tumors. Herein, we report a case of ITTC diagnosed by fine-needle aspiration cytology (FNA). A 55-year-old male presented with a slowly increasing cervical mass. Cervical ultrasonography revealed an irregular mass measuring 3.7 × 2.5 × 2.1 cm. FNA was performed. Cytological findings showed that the tumor was highly cellular and tumor cells were arranged in islet-like clusters accompanied by lymphocytes. The tumor cells had a high nuclear-to-cytoplasmic ratio. The nuclei were round to ovoid or spindle-shaped. The fusiform tumor cells exhibited a regular streaming arrangement, similar to squamous cell carcinoma. Immunocytochemically, the tumor cells were positive for CD5 and c-KIT. Pathological examination of the resected thyroid specimen revealed confluent cell nests of epithelioid and spindle cells with significant lymphocyte and plasma cell infiltration throughout the tumor. Immunohistochemically, the tumor cells were positive for cytokeratin, CD5, c-KIT, and p63, and negative for TTF-1 and thyroglobulin. Therefore, the tumor was diagnosed as ITTC. Although ITTC is rare, it should be considered in the differential diagnosis of a mass in the lower pole of the thyroid gland that exhibits large cohesive islet-like clusters with numerous lymphocytes and features resembling those of squamous cell carcinoma.
甲状腺内胸腺癌（ITTC）是一种罕见的甲状腺恶性肿瘤，类似于胸腺上皮相关肿瘤。在此，我们报告一例经细针穿刺细胞学检查（FNA）确诊的ITTC病例。一名55岁男性患者出现颈部肿块，且肿块逐渐增大。颈部超声检查发现一个不规则肿块，大小为3.7×2.5×2.1cm。进行了FNA检查。细胞学检查结果显示肿瘤细胞丰富，肿瘤细胞呈胰岛样簇状排列，并伴有淋巴细胞。肿瘤细胞的核质比高。细胞核呈圆形至卵圆形或梭形。梭形肿瘤细胞呈规则的流线状排列，类似于鳞状细胞癌。免疫细胞化学检查显示，肿瘤细胞CD5和c-KIT呈阳性。对切除的甲状腺标本进行病理检查，发现上皮样细胞和梭形细胞融合成巢状，整个肿瘤有明显的淋巴细胞和浆细胞浸润。免疫组织化学检查显示，肿瘤细胞细胞角蛋白、CD5、c-KIT和p63呈阳性，甲状腺转录因子-1（TTF-1）和甲状腺球蛋白呈阴性。因此，该肿瘤被诊断为ITTC。尽管ITTC罕见，但在鉴别诊断甲状腺下极出现的、表现为大的紧密胰岛样簇状且有大量淋巴细胞以及具有类似鳞状细胞癌特征的肿块时，应考虑到该病。
