A 7-y-old backyard Leghorn chicken (Gallus domesticus) was submitted to the California Animal Health and Food Safety Laboratory System (CAHFS)–Turlock branch for postmortem examination, with a history of unexpected death. At postmortem examination, a hemorrhagic soft tissue mass was observed in the cervical region. Microscopically, a densely cellular neoplasm of polygonal epithelial cells and small lymphocytes was observed. The microscopic features of the neoplasm in combination with positive immunohistochemistry for pancytokeratin and CD3 were used to classify the lesion as a thymoma. Thymoma was diagnosed in only 5 birds submitted to CAHFS from 1990 to 2019. Thymoma has been described only rarely in birds, and is an unusual diagnosis in backyard chickens.

一只 7 岁的后院来亨鸡 ( Gallus domesticus ) 被提交给加州动物健康和食品安全实验室系统 (CAHFS)-Turlock 分公司进行尸检，有意外死亡史。尸检时，在颈部区域观察到出血性软组织肿块。显微镜下观察到由多角形上皮细胞和小淋巴细胞组成的致密细胞肿瘤。肿瘤的微观特征结合泛细胞角蛋白和CD3的阳性免疫组织化学被用于将病变分类为胸腺瘤。从 1990 年到 2019 年，只有 5 只提交给 CAHFS 的鸡被诊断出胸腺瘤。胸腺瘤在鸟类中很少被描述，并且在后院鸡中是一种不寻常的诊断。