Ovarian tumors in mares are uncommon in comparison to other neoplasms and are classified into three categories: gonadal stromal tumors, coelomic epithelium surface tumors, and germinal cell tumors. Some ovarian neoplasms histologically show a mixture of multiple cell types in the same tumor, such as fibrothecoma; therefore, the differentiation between fibroma and thecoma is often difficult. According to the World Health Organization, fibrothecomas are classified as sex-cord stromal tumors (pure stromal tumors). Neoplasms such as fibrothecoma present with limited morphological, clinical, ultrasonographic, and endocrine profile characteristics. To diagnose this type of tumor, a broad clinical examination is needed, but histopathology remains the most accurate. Herein, we report a case of incidentally found ovarian fibrothecoma during a diagnostic laparotomy in a 6-year-old Dutch Warmblood (KWPN) mare who presented to the clinic with colic symptoms. After a unilateral ovariectomy, the altered right ovary was diagnosed as fibrothecoma based on histopathological features.
Keywords: fibrothecoma; histopathology; neoplasia; ovarian tumor.