Received: 21-07-2017 / Accepted: 02-07-2018
Leydig cell tumor is one of the most common testicular tumors in dogs. The objective of the present study was to examine the clinicopathologic and immunohistochemical features of canine Leydig cell tumor. Testicular tumors (Leydig cells) were found in the testicles of six dogs in veterinary clinics in Hanoi. Clinical symptoms included swelling, hyperpigmentation on the scrotal skin and/or hematuria, perineal hernia, and squatting to urinate. The tumors were macroscopically small, yellow to brown, soft and sharply demarcated with hemorrhage or cysts on cross-section. Microscopically, all cases show a similar histological appearance, being composed of round to polygonal cells with (or without) fine vacuoles in pale, abundant eosinophilic cytoplasm, a small and round eccentric nucleus, and infrequent mitotic figures. Neoplastic cells, in solid sheets (100%), angiomatoid (66.67%) or pseudo-adenomatous (50%) pattern, frequently contained testicular degeneration, lipid accumulation, hemorrhage and cystic structure. Immunohistochemically, tumor cells in all cases were positive for vimentin, inhibin-, melan-A and E-cadherin, but negative for neuron-specific enolase (NSE). These results help in the education and diagnosis of canine Leydig cell tumor and support future studies of tumor in animals.