Gastrointestinal stromal tumors in a baboon, a spider monkey, and a chimpanzee and a review of the literature

Gastrointestinal stromal tumors (GISTs) are believed to originate from the intestinal pacemaker cells (interstitial cells of Cajal) or their progenitor cells. Spontaneous tumors have been reported in dogs, horses, rhesus, and a chimpanzee and they have been produced experimentally in mice and rats. GISTs represent a diagnostic challenge because they cannot be differentiated from non-lymphoid mesenchymal tumors without using human c-kit (CD117) immunohistochemistry. Three neoplasms were incidental findings at necropsy in the stomachs of a baboon and a spider monkey and in the rectum of a chimpanzee. The GISTs were initially diagnosed grossly and histologically with hematoxylin and eosin as leiomyomas. Immunohistochemical analysis revealed that all three were c-kit (CD117) positive. These are the first reports of GISTs in the baboon and spider monkey and the second in a chimpanzee. The occurrence of GISTs in non-human primates may provide a unique opportunity to study these tumors.