Cytomorphology of gastrointestinal stromal tumor: diagnostic role of aspiration cytology, core biopsy, and immunochemistry

Gastrointestinal stromal tumors (GISTs) comprise a heterogeneous group of neoplasms of the gastrointestinal tract previously referred to as leiomyomas, leiomyosarcomas, or schwannomas. GISTs derive from the interstitial cell of Cajal and, in addition to variable expression of smooth muscle and neural markers, they characteristically express CD34 and CD117. To our knowledge, the cytologic appearance of gastric neoplasms designated as GISTs has never been reported. We illustrate the fine-needle aspiration (FNA) cytology findings of a gastric stromal tumor having spindle cells with delicate cytoplasm and prominent nuclear palisading. Consistent core biopsy and immunochemistry findings further supported the diagnosis of GIST. Pathologic evaluation of the resected tumor confirmed the cytologic diagnosis. In the appropriate clinical and radiologic setting, a confident diagnosis of GIST can be established by FNA cytology and core biopsy. The roles of immunochemical stains and other ancillary techniques in reaching the correct diagnosis are addressed.