Tumours of the ovary.

Ovarian tumours are common in animals, the majority occurring in bitches and cows. The two most important germ cell tumours were dysgerminoma and teratoma; these morphologically resemble their counterparts in women, with the exception that teratomas in animals tend less to malignancy. The granulosa cell tumour is the most frequent sex cord-stromal tumour in all six species and it may contain luteinized areas or show differentiation towards a Sertoli cell pattern. The canine papillary adenoma and papillary adenocarcinoma, which are as common as granulosa tumours, have several features in common with their counterparts in women: they are of similar histological appearance, are frequently bilateral, and the adenocarcinomas have a great propensity for peritoneal implantation metastasis. Ovarian cysts are frequent in the bitch, sow, and cow and may originate from five different anatomical structures in the ovary.