Intestinal myxosarcoma in a thoroughbred mare.

A thoroughbred mare with chronic colic and weight loss was diagnosed with a myxosarcoma in the intestinal tract, a rare occurrence in horses, which was deemed inoperable because of its location and the difficulty in removing it surgically.

Background of the Study

• The study begins with a thoroughbred mare exhibiting chronic signs of colic and weight loss. As these symptoms persisted, a surgical exploration of the mare’s abdomen was carried out to determine the underlying cause.

Findings

• Upon surgical exploration, a substantial fibrotic mass was discovered originating from the base of cecum, a part of the large intestine. The mass was protruding into the intestinal passageway, partially obstructing it.
• Due to the location of the mass and the inability to adequately externalize it from the mare’s abdominal cavity, surgical removal was deemed impossible.
• Upon examination, the mass was found to be fibrous and contained a shiny, gelatinous material throughout—it was identified as a neoplasm, or new abnormal growth of tissue.
• Further histological analysis discovered large spaces filled with mucopolysaccharides within the mass, as identified through staining with Alcian blue—an acidic dye used to demonstrate acidic substances in tissues.

Diagnosis

• Based on the presence of atypical fibroblastic cells—cells responsible for producing the structural framework of animal tissues—and a mucinous stroma, which is a segment of connective tissue in tumors, combined with local invasiveness and metastasis to regional lymph nodes, the mass was diagnosed as a myxosarcoma.
• Myxosarcoma is a rare connective tissue cancer that’s characterized by the presence of mucopolysaccharides within the tumor. Mucopolysaccharides are long chains of sugar molecules that are found throughout the body and are often affected in some types of cancer.

Significance

• The case study is notable because myxomatous tumors, including myxosarcomas, have never been documented in the equine intestinal tract before. This study therefore marks a significant discovery in equine medicine.