ABSTRACT
We would like to report a case of leiomyoma of the ovaries in a dog. Leiomyoma is commonly seen in the vagina in dogs. However, it is a very rare neoplasm in the ovaries. As there have only been a few reported cases, this report provides valuable information on veterinary medicine and pathology. Masses found in the ovaries need to be differentiated from other ovarian tumors. Therefore, we describe the gross, histopathological, and immunohistochemical features of a case of ovarian leiomyoma in a 10-year-old female Yorkshire Terrier dog. The mass on the right of the uterus was found accidentally by pelvic ultrasonography. Laparatomy revealed a large multi-nodulated ovarian mass. Grossly, cut surfaces of the mass showed multiple firm whitish nodules in the cortex and bloody loose connective tissue in the medulla. Histopathologically, the cortex of the mass was composed of spindle cells forming interlacing fascicles. The cells had elongated, blunt-ended nuclei and eosinophilic cytoplasm as detected by hematoxylin and eosin staining. Immunohistochemical stained sections were immunoreactive for alpha-smooth muscle actin and desmin but negative for vimentin and S-100. Therefore, differential diagnosis confirmed leiomyoma based on morphology and positive staining for alpha-smooth muscle actin and desmin.