Clinicopathological features of an equine ovarian teratoma.

This research article explores the unique case of a mature ovarian teratoma, a type of tumor, in a young Andalusian mare (horse), and discusses its clinical and pathological features.

Initial Findings and Procedure

• The study discusses an abnormal mass that was discovered in the left ovary of a four-year-old, cyclic, nulliparous Andalusian mare during a breeding soundness examination. Nulliparous indicates that the horse had never given birth.
• The researchers noted the mass was hard with various echogenic properties, leading them to perform laparoscopy, a minimally invasive surgical procedure, to confirm a neoplastic change. Neoplastic change refers to the abnormal growth of cells, which can indicate the presence of a tumor.
• Post confirmation, they carried out a unilateral laparotomic ovariectomy, a surgical procedure where one ovary was removed while the animal was standing.

Teratomatous Ovary Analysis

• The cut surface of the teratoma displayed a large follicular cyst filled with hair and sebaceous material and three smaller cysts containing mucous fluid. These were surrounded by solid areas where bone and cartilage were seen. This suggests that the teratoma was a mature one, composed of various types of tissue.
• Interestingly, parts of the ovary remained functional, with small follicles and a diestral corpus luteum found near the tubal extremity. This is the part of the ovary responsible for releasing eggs and hormonal secretion during a mare’s estrous cycle.

Histology Results

• A histological examination of the teratoma revealed the presence of a variety of mature tissues not typically found in the ovary. These included stratified squamous and respiratory epithelia (skin and lining of the respiratory tract cells), mucous, sweat and sebaceous glands (glandular tissues), muscle fibers, fat, and nervous tissue.
• At times, the structure of tracheal and lung tissues was observed, indicative of the teratoma’s complex nature.

The study provides an insightful understanding of the clinical and pathological aspects of mature ovarian teratomas in equine species. They highlight the diversity of tissues that can be seen in teratomas and recognize the peculiar presence of functioning ovarian remnants in such conditions. The findings can serve as a useful reference for future instances of similar neoplastic conditions in equine species.