arabian

Background: A Grey 12-year-old Arabian endurance horse gelding was referred to the SHS Veterinary Center for anorexia, mild colic of 5 days duration, and melena of 1 day duration. The owner reported recurring colic, 12 episodes of mild colic in the previous year. Methods: On admission, vital signs were within normal limits and body condition score was estimated to be 3/9. Results: Packed cell volume (PCV) was 28% [reference range (RR): 31% to 47%] and plasma total protein was 58 g/L (RR: 60 to 80 g/L). Hematochezia was observed. Abdominal ultrasound examination detected no abnormalities. Over the next 12 h, the horse experienced hematochezia and several mild episodes of colic and death. A necropsy was performed. A mass arising from the right dorsal ascending colon near the base of the cecum and extending transmurally from the colonic mucosa into the mesocolon was a 8 cm × 5 cm × 8 cm firm, homogenous, tan mass. The portion of the mass that extended into the colonic lumen was pedunculated, with an ulcerated surface. The adjacent segments of colon were markedly reddened and edematous. Histologically, the mass was comprised of large interweaving sheets of small, spindle cells with ill-defined cell borders embedded in abundant myxomatous matrix. Tumor cells contained scant eosinophilic cytoplasm and oval to elongate nuclei with finely stippled chromatin and inconspicuous nucleoli. Mitotic figures were rare (1/10) high power fields. Tumor infiltrated between the muscularis interna and the muscularis externa at the myenteric plexi. Conclusion: Gross and histologic appearance, were consistent with a diagnosis of gastrointestinal stromal tumor.