Imaoka Masako, Osawa Tetsuya, Kai Kiyonori, Tsuchiya Yoshimi
Medicinal Safety Research Laboratories, Daiichi Sankyo Co., Ltd., 16-13 Kita-Kasai 1-Chome, Edogawa-ku, Tokyo 134-8630, Japan.
J Toxicol Pathol. 2022 Jul;35(3):263-268. doi: 10.1293/tox.2022-0018. Epub 2022 May 7.
A 104-week-old male CD (SD) rat exhibited enlargement of the left testis. Microscopically, this mass was demarcated from the testis by fibrous connective tissue and characterized by cystic dilatation with single-layered columnar cells and papillary proliferation connected to the solid growth area without clear boundaries. In the solid growth area, cells were dissected into irregular alveolar nests by scant fibrous tissue with small blood vessels. The nuclei of proliferating cells were variable in size and round- to oval-shaped, and their cytoplasm was pale or eosinophilic and sometimes contained vacuoles or eosinophilic granules. Immunohistochemically, the tumor cells were positive for vimentin and cytokeratin (CK) 7. Since CK7 was exclusively positive in the rete testis epithelium of the naïve rat, it was valuable to diagnose this tumor as rete testis-originated. Based on these results and the lack of apparent pleomorphism, mitotic figures, and metastasis, the present case was diagnosed as rete testis adenoma.
一只104周龄的雄性CD（SD）大鼠出现左侧睾丸肿大。显微镜下，该肿物由纤维结缔组织与睾丸分界，其特征为囊性扩张，内衬单层柱状细胞，并有与实性生长区域相连的乳头样增生，边界不清。在实性生长区域，细胞被少量带有小血管的纤维组织分隔成不规则的腺泡巢。增殖细胞的细胞核大小不一，呈圆形至椭圆形，其细胞质淡染或嗜酸性，有时含有空泡或嗜酸性颗粒。免疫组化显示，肿瘤细胞波形蛋白和细胞角蛋白（CK）7呈阳性。由于CK7仅在正常大鼠的睾丸网上皮中呈阳性，因此将该肿瘤诊断为睾丸网起源具有重要意义。基于这些结果以及缺乏明显的多形性、核分裂象和转移，本病例被诊断为睾丸网腺瘤。
