Uterine Leiomyosarcoma in a Lion-Head Rabbit

A 5-year-old female lion-head rabbit weighing 2 kg was brought to a local animal hospital with hematuria. Radiography showed a mass in the uterus, which was removed by ovariohysterectomy. Macroscopic examination showed several masses in both uterine horns. These masses, which invaded the deep uterine walls, were firm to the touch, and their cut surfaces were greyish-white in color. Histopathologically, these masses were nonencapsulated and were composed of spindle cells arranged in cellular, large interlacing bundles or streams. The tumor cells had elongate nuclei with prominent nucleoli, granular chromatin and eosinophilic cytoplasm. Moderate anisocytosis and anisokaryosis were observed. Severe and extensive inflammation and necrosis were present within the masses. Immunohistochemically, the neoplastic cells were positive for vimentin, desmin, and α-smooth muscle actin, but negative for cytokeratin. These uterine masses were diagnosed as leiomyosarcoma. To our knowledge, this is the first report of a uterine leiomyosarcoma in the rabbit in Korea.