Chondroblastic osteosarcoma of the middle ear in a guinea pig .

A 3-year-old intact female guinea pig was presented for acute anorexia. Medical and surgical treatments for cystitis and ovarian cysts, respectively, did not prevent continuous weight loss. Computed tomography and histopathological analysis revealed a chondroblastic osteosarcoma of the right middle ear, which has not been reported in this species.