Myofibromas are mesenchymal tumours of myofibroblastic origin that occur in solitary or multicentric forms. Solitary benign myofibromas mainly occur on the head and neck, especially in the subcutaneous region. They rarely occur in visceral organs in humans, but visceral myofibroma has not been reported in animals. We now report a case of testicular myofibroma in a 6-year-old rabbit in which orchiectomy revealed an enlarged testis with a multinodular surface. The cut surface of the testis showed a thick, homogeneous white–yellow mass surrounding the testicular parenchyma. Histopathologically, the mass was composed of collagen and eosinophilic fascicles of spindle cells that were immunopositive for α-smooth muscle actin but not desmin, S-100 or von Willebrand factor. These features distinguished the myofibroma from other spindle cell tumours. To the best of our knowledge, this is the first report of solitary testicular myofibroma in any animal species.

肌纤维瘤是肌纤维母细胞起源的间充质肿瘤，以单发或多中心形式发生。孤立性良性肌纤维瘤主要发生在头颈部，尤其是皮下区域。它们很少发生在人类的内脏器官中，但尚未在动物中报告内脏肌纤维瘤。我们现在报告一例 6 岁兔子的睾丸肌纤维瘤，其中睾丸切除术显示睾丸增大并具有多结节表面。睾丸切面显示睾丸实质周围有一厚厚均匀的白黄色肿块。组织病理学上，肿块由胶原蛋白和梭形细胞嗜酸性束组成，这些梭形细胞对 α-平滑肌肌动蛋白呈免疫阳性，但对结蛋白、S-100 或 von Willebrand 因子无免疫阳性。这些特征将肌纤维瘤与其他梭形细胞肿瘤区分开来。