Malignant mesenchymal tumours are only rarely reported in turtles. In the present case, an 8-year-old female common musk turtle (Sternotherus odoratus) was presented with a solid, reddened, non-mobile mass on the right forelimb. The mass had a thin, membranous lining and a grey–white cut surface. Histological examination revealed a cell-rich, focally infiltrative neoplasm consisting of spindloid tumour cells arranged in bundles and streams. Rarely, indistinct cytoplasmic cross-striations were seen in the neoplastic cells. Transmission electron microscopy revealed cytoplasmic, disorganized muscle fibrils and haphazardly arranged, attenuated Z-lines in the neoplastic cells. The histological, histochemical and ultrastructural findings led to the diagnosis of a rhabdomyosarcoma. This is the first description of rhabdomyosarcoma in a freshwater turtle.

恶性间充质肿瘤在海龟中很少报道。在本案中，一只 8 岁雌性麝香龟（Sternotherus odoratus) 出现在右前肢上有一个实心的、发红的、不可移动的肿块。肿块有薄的膜状内衬和灰白色切面。组织学检查显示细胞丰富的局灶性浸润性肿瘤，由呈束状和流状排列的纺锤体肿瘤细胞组成。罕见地，在肿瘤细胞中可见模糊的细胞质横纹。透射电子显微镜显示肿瘤细胞中的细胞质、杂乱无章的肌肉原纤维和随意排列的减弱的 Z 线。组织学、组织化学和超微结构结果导致横纹肌肉瘤的诊断。这是对淡水龟横纹肌肉瘤的首次描述。