Bilateral low grade serous adenocarcinoma of the ovaries in a badger (Meles meles L.) and its association with a borderline serous ovarian tumour: a case report

Here, we describe a case of a wild female badger (a sow) with disseminated serous adenocarcinoma of the ovary which corresponds to a group of low grade serous carcinomas of the ovary in humans. Beside grossly apparent dissemination of the disease we observed a scale of histological features classifiable as a precursor lesion - borderline serous tumour of the ovary with implant metastases at the peritoneum, and features of the borderline tumour transformation in the carcinoma. The latter features included invasion of some of the metastatic peritoneal implants into the adipose tissue of the mesentery, retroperitoneum, and in the muscle of diaphragm with lymphangioinvasion and with blood-borne metastatic disease in the lungs. The primary tumour and its metastases had a uniform cytological appearance without atypia of the tumour cells. Mitotic activity was exceptional. The proliferation activity as demonstrated by immunohistochemical investigation of Ki-67 protein expression (revealing all active phases of the cell cycle - G1, S, G2, M) showed a low proliferation activity of the tumour cells, comparable with findings in low grade carcinomas or borderline tumours of the ovaries in women. WT1 protein was expressed in the whole tumour cell population. All these features were diagnostic of serous carcinoma of the ovary with low grade malignant potential. Tumours of the ovaries in wildlife have been described previously but they are infrequent and are rarely classified histopathologically. This case report offers a parallel with serous carcinomas in human pathology including features of transformation from a precursor lesion of a borderline serous tumour into a serous low grade carcinoma.