Abstract

Colonic gastrointestinal stromal tumors (GISTs) are rare and behave aggressively compared to GISTs in other parts of the gastrointestinal tract. Therefore, accurate diagnosis of GISTs and their distinction from other mesenchymal tumors is important for proper patient management and follow-up. Herein, we present an unusual case of a colonic GIST mimicking an inflammatory fibroid polyp with a novel 63 bp deletion mutation in exon 11 of the c-kit gene, which has not previously been reported. The tumor consisted of loosely arranged spindle cells and many inflammatory cells scattered throughout the tumor. Immunohistochemically, the tumor cells were focally and weakly positive for c-kit and diffusely positive for CD34, but were negative for PKC-theta, SMA, S-100 protein, ALK-1, and desmin. Our case re-emphasizes the broad morphologic spectrum of GISTs.

• Keywords: Gastrointestinal stromal tumors;Colonic polyp;c-kit;Mutation