Metastasising granulosa cell tumour of the testis: A case report in the dog

A 10-year-old Italian Spitz dog was admitted for a right inguinal swelling. On scrotal palpation, the right testis was lacking and a large, firm, mass, with an irregular shape and overdistended skin, was found lateral to the penis. On ultrasonography, a solid, lobulated neoplasm could be seen, showing multiple hypoechoic cysts and interposed hyperechoic septa. Grossly, the excised
testis was enlarged presenting a nodular surface, non-homogeneous consistency and haemorrhagic areas. The cut surfaces had a complete replacement by neoplastic tissue, with different sized cysts, containing serous-haemorrhagic fluid. Histologically, the cystic structures resembled Graafian follicles,
whose fibrous walls were lined by several layers of granulosa-like cells, with occasional pseudo-papillary projections and Call-Exner bodies. These findings were consistent with a diagnosis of malignant testicular granulosa cell tumour. Six months after surgery, the dog showed weakening, abdominal enlargement, difficulty in walking and urinating. Physical and ultrasonographic examinations showed ascites and a very large, firm, abdominal mass. At laparotomy it invaded most of the abdominal cavity and euthanasia was necessary. Histology confirmed the same nature of the testicular tumour. Testicular granulosa cell tumour is extremely rare in canine literature and no malignant cases have been reported.