Gastrointestinal stromal tumors (GISTs) arise from the intestinal pacemaker cells, interstitial cells of Cajal,2 and are the most common mesenchymal neoplasm in the gastrointestinal tract.4 However, they still comprise only 5% of all sarcomas. GISTs have been extensively studied in humans but have only been reported in a few additional species including four species of non-human primates.1 A 35-year-old brown-headed spider monkey (Ateles fusciceps) was diagnosed with a GIST as an incidental finding when she underwent exploratory laparotomy for an unrelated condition. At the time of diagnosis, the nodule was approximately 5 mm in size and was completely excised. The tumor was found to be spindlyloid and have a relatively low mitotic index of 5/hpf. As 70–80% of GISTs involve mutations in KIT protein (a tyrosine kinase receptor expressed on the surface of the cells), recommended therapy for GISTs includes surgical excision followed by chemotherapy using tyrosine kinase inhibitors.3 An oncologist was consulted in this case and due to the relatively low mitotic index, small size of the tumor, and the early detection, it was decided to avoid chemotherapeutics and simply monitor for progression of disease via quarterly abdominal ultrasounds. No evidence of metastasis or recurrence has been found to date (18 months). This is the first report of antemortem diagnosis and follow-up of a GIST in a spider monkey.
The authors would like to thank Upstate Veterinary Specialists in Greenville, SC, for their prior assistance in the medical and surgical management and their continued assistance in the follow-up of this case.
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