Bilateral ovarian adenocarcinoma in a mare causing haemoperitoneum and colic.

The study is about a case of a 13-year-old mare diagnosed with bilateral ovarian adenocarcinoma which led to severe abdominal bleeding and painful digestion issues. The study documents this rare instance in the equine medical community and encourages further investigation of the differentiation of ovarian and intestinal adenocarcinoma in horses.

Case Presentation

• A 13-year-old Thoroughbred mare was brought to Massey University Veterinary Teaching Hospital due to severe severe colic symptoms which couldn’t be alleviated with painkillers.
• An examination revealed a high heart rate at 100 beats per minute and the horse’s mucous membranes were noticeably pale and sticky, indicating poor circulation.
• Further physical examination identified a large mass in the lower left abdomen by transrectal palpation, raising concern of a tumor or other significant medical concerns.

Explorative Laparotomy

• An explorative laparotomy, a surgical procedure to investigate the contents of the abdomen, was performed and revealed severe haemoperitoneum, or blood in the abdominal cavity.
• Several tumor-like masses were found in connection with the reproductive tract, leading to euthanasia of the mare due to poor prognosis.

Post-mortem Examination

• On post-mortem examination, the masses were found to be directly attached to both ovaries and exhibited similar masses in the omentum (a prominent fatty layer in the abdomen), and the peritoneal surface of the diaphragm, spleen, and liver.
• Under histopathology study, it was found that these masses comprised of disorganized proliferating cuboidal to columnar cells separated by dense collagenous stroma, indicative of a type of cancer known as adenocarcinoma.
• Immunohistochemistry results showed that these cancer cells were positive for cytokeratin AE1/AE3 and vimentin, but negative for cytokeratin 7 and inhibin α. This helped further define the type and structure of the cancer cells.

Conclusion and Implication For Future Research

• The mare was diagnosed with bilateral ovarian adenocarcinoma, a form of cancer that hadn’t been previously documented in horses.
• The rupture of one of these neoplastic masses was the likely cause of the horse’s haemoperitoneum and ultimate decompensation.
• The authors emphasized that similar cases of ovarian adenocarcinoma should be considered when horses present similar symptoms of abdominal bleeding and colic.
• This raises a need for further research, specifically in the area of the immunohistochemical differentiation of adenocarcinoma of ovarian and intestinal origin in horses.