A planar gastrointestinal stromal tumor replacing the proper muscle layer causing fecaloma and perforation in the sigmoid colon: a case report and literature review.

A 72-year-old Japanese male with acute abdomen underwent emergency surgery for a preoperative diagnosis of stercoral colonic perforation of the sigmoid colon. A pathological examination revealed a proliferating spindle cell lesion that surrounded the perforation and replaced the muscularis propria without any mass formation. The spindle cells were positive for KIT and CD34 by immunohistochemistry, and somatic mutation of the c-kit gene was found using genomic DNA extracted from the lesion. We diagnosed the spindle cell lesion as a planar gastrointestinal stromal tumor (GIST). We speculate that perforation of the sigmoid colon in this case may be caused by the stasis of stool resulting from abnormal peristalsis of the lesional site. Two other similar cases have been reported in the literature, and showed good prognoses. Although their pathogenesis is unclear, planar GISTs should be considered as a possible cause of idiopathic or stercoral colonic perforation.