Malignant Sertoli cell tumour in a young Simmenthal bull--clinical and pathological observations.

Tumours are rare in the bovine testicle. A case of malignant Sertoli cell tumour in a 29-month-old Simmenthal bull that was hospitalized with a history of severe unilateral scrotal swelling is reported. On inspection and palpation, the scrotal sac was found enlarged with fluctuant content in the right side. The right testicle was enlarged, hard and indolent. Also the right plexus pampiniformis and funiculus spermaticus were enlarged. Sonograms revealed severe changes in the right testicle with a loss of homogeneity and multiple hyperechogenic areas. After slaughter, the scrotum with testicles were removed and evaluated pathologically. On section, the right testicle contained areas of necrosis, haemorrhage, and mineralization. Histology showed Sertoli cells in tubular structures surrounded by dense fibrous stroma replacing normal testicular tissue. Both lymphatic and blood vessels were infiltrated by neoplastic cells. Immunohistochemically, the neoplastic cells stained positive for vimentin and negative for cytokeratin and S-100. Based on the pathological observations a diagnosis of right-sided malignant Sertoli cell tumour with vascular invasion and hydrocele was established.