Poorly differentiated leiomyosarcoma of the urogenital tract in a horse.

The research presents a case of leiomyosarcoma, a rare type of cancer, affecting the urogenital tract of a young female horse. This cancer led to severe health complications including suppression of normal urogenital structures and difficulty in urination, and eventually necessitated the euthanasia of the animal.

Case Presentation

• The research focuses on a case of a 2-year-old Thoroughbred filly (a young female horse) who was observed to have bleeding from the vulva and suspected hematuria (presence of blood in urine) persisting over five days.
• Initial tests ruled out a primary coagulopathy (a condition affecting the blood’s ability to coagulate and form clots), suggesting that the bleeding could be caused by something else.
• Further investigations using vaginoscopy and cystoscopy uncovered a large, bleeding mass in the bladder that extended into the vagina, causing severe distortion of the normal urogenital structures and making urination difficult for the horse.

Diagnosis

• An endoscopic and surgical biopsy were conducted, and histologic examination of the tissue samples showed a poorly differentiated neoplasia (growth or tumor resulting from abnormal and excessive cell division) indicating it likely originated from mesenchymal tissue (connective tissue from which many tumors originate).
• The horse was also diagnosed with chronic suppurative cystitis (a long-lasting inflammation of the bladder characterized by the accumulation of pus), caused by the bacteria Streptococcus zooepidemicus.

Treatment and Outcome

• Despite treatment with the chemotherapy drug doxorubicin, the tumor continued to grow and caused considerable discomfort and stranguria (painful and frequent urination) in the horse.
• Due to the severity of the case and the bleak prognosis, the decision was made to euthanize the horse.
• A post-mortem examination revealed that the tumor had caused extensive damage to the urinary bladder and had spread to the broad ligament of the uterus.
• The mass was confirmed through histologic examination and immunohistochemical staining for alpha-actin (a protein commonly found in muscle tissue) to be a poorly differentiated leiomyosarcoma (a rare and aggressive type of cancer that arises from smooth muscle cells).

Conclusions

• The findings from this case suggest that leiomyosarcoma should be considered as a potential diagnosis in horses presenting with unexplained urogenital bleeding.