Abstract
Adenomatous hyperplasia of the rete ovarii was found in a 9-month-old beagle. At necropsy, no abnormalities were observed in the ovaries. Microscopically, there was a proliferation of gland-like tubules in the hilus of the left ovary. The tubules were lined by a single layer of columnar and cuboidal epithelial cells. In places the tubules appeared to radiate from small ductal structures. The lesion was poorly demarcated and blended with the existing tubular architecture of the rete ovarii, and extended diffusely into the adjacent stroma. Immunohistochemistry showed positive reactions for cytokeratin 18 and vimentin, suggesting that the lesion was derived from the rete epithelia with proliferative activity.
