Proventricular and ventricular gastrointestinal stromal tumor (GIST) in a scarlet macaw (Ara chloropterus)

Abstract

GISTs can be benign or malignant, and they have been reported in a wide variety of species, including humans, non-human primates, dogs, and cats; however, reports of this tumor in birds are rare. These neoplasms are seen in the gastrointestinal tract and are derived from the Cajal Cells responsible for regulating gastrointestinal motility. We report a case of a gastrointestinal stromal tumor in a scarlet macaw (Ara chloropterus) that was referred to necropsy at the Veterinary Hospital of the Federal University of Paraíba (UFPB), Northeastern Brazil. Macroscopically, the proventriculus and ventriculus were dilated, and the walls of both organs were thickened by a firm, ulcerated mass covered by fibrin strands. In the histopathology, the proventriculus presented an expansive, non-encapsulated neoplasm formed by homogeneous spindle cells, with eosinophilic cytoplasm, indistinct borders, mild to moderate pleomorphism, and rare mitotic figures, being suggestive of a leiomyoma. In immunohistochemistry, a positive multifocal immunolabeling for the C-KIT proto-oncogene was observed in the cytoplasm of neoplastic spindle cells, thus compatible with a gastrointestinal stromal tumor (GIST). The occurrence of GISTs in avian species might have been overlooked, and the authors recommend that previously reported gastrointestinal leiomyomas or leiomyosarcomas be tested for this immunomarker to rule out the possibility of GISTs.