Testicular granular cell tumor and metachronous biliary adenoma in a domestic rabbit (Oryctolagus cuniculus)

A nine-year-old intact male domestic rabbit (Oryctolagus cuniculus) was presented with an enlarged left testis. Following surgical castration, histopathologic examination of the affected testis revealed a granular cell tumor. The tumor cells tested positive for PAS and Melan A. Testicular hypoplasia was diagnosed in the contralateral testis. The animal recovered uneventfully. More than a year later, the animal died from unrelated cause. Necropsy revealed a hepatic neoplasm, along with pulmonary and renal changes. There was no evidence of metastasis from the testicular granular cell tumor. Microscopic examination identified a biliary adenoma with multifocal biliary hyperplasia in the liver, moderate interstitial pneumonia, hyperplastic changes in the pulmonary arterial blood vessels, and end stage kidney disease. This case report supports existing literature indicating that testicular granular cell tumors in rabbits are benign and that surgical castration is curative. It remains unclear whether hypoplasia of the contralateral testis influenced neoplastic proliferation. The biliary adenoma was an incidental necropsy finding and could have progressed from biliary hyperplasia.