Diagnosis and surgical management of ovarian tumours in the mare

During a four year period (1996-1999), 31 mores underwent an unilateral ova riectomy as a result of the diagnosis of ovarian neoplasia. The diagnosis w as based on the results of behavioural control, clinical, ultrasonographica l and endocrinological (circulating levels of T, E-2, P-4) examination adde d by collection and patho- and immunohistological examination of endometriu m biopsy specimens. Typical findings in mores with postoperatively confirme d granulosa cell tumour included stallion like behaviour, unilateral enlarg ement of the affected ovary with atrophy of the inhibited contralateral ova ry and abnormality in different variations in the ultrasonographical appear ance of the neoplastic ovary. Prior to ovariectomy serum testosterone level s were remarkably elevated in 13 of the 31 mores. Surgical procedures inclu ded flank approach by modified grid technique or ventral midline approach w ith exteriorization and complete resection of the effected ovary under gene ral anesthesia. Pathohistological examination of the 31 ovaries revealed 28 granulosa cell tumours, one thecoma, one cystadenoma and one malignan tera toma. With only one exception, even clinically and endocrinologically uncle ar remaining granulosa cell tumours were associated with an irregular endom etrial differentiation (IED) possibly indicating a hormonal activity of the tumour cells. The teratoma and the cystadenoma did not affect the endometr ial differentiation. Irregular endometrial differentiation may indicate hormonal disturbances du e to ovarian neoplasia and serves as a distinct bio essay which is availabl e prior to surgery. In addition to clinical, ultrasonographical and endocri nological findings, endometrial biopsy is a useful aid in the evaluation of abnormal ovaries.