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

A metastasising testicular granulosa cell tumour was observed in a 10 years old Italian Spitz dog. The tumour arose in the right ectopic testis. On section surfaces the testis was completely replaced by neoplastic tissue including solid and cystic areas. Histology showed follicle-like structures, lined with higly pleomorphic tumour cells resembling the ovarian granulosa cells. Six months later the dog was re-examined and ascites and an extensive abdominal mass were found. At explorative laparotomy an inoperable multicentric abdominal mass was recognized and the dog was euthanasized. Light microscopy revealed extensive metastatic tumour lesions. The present report is the first documented case of metastasising granulosa cell tumour of the canine testis with an unusual highly aggressive behaviour.