A case of planar-type gastrointestinal stromal tumor of the transverse colon with perforation.

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumor of the human gastrointestinal tract. They usually develop in the stomach and small intestine, but extremely rarely in the colon. Although most GISTs form a mass, some cases showing a flatly proliferating lesion called planar-type GIST have been reported in the sigmoid colon and small intestine. Those are often associated with diverticular lesion and/or perforation. We present here a case of planar-type GIST of the transverse colon with perforation. A 49-year-old Japanese woman abruptly complained of abdominal pain, and was clinically diagnosed as perforation of the transverse colon. Partial resection of the transverse colon including the perforated site was done, and no apparent mass lesion was present. Histology showed that spindle cells flatly proliferated around the perforated area and replaced the layers from submucosa to subserosa. Immunohistochemistry revealed that the spindle cells were KIT-, DOG1- and CD34-positive. Codons 557 and 558 of exon 11 of the c-kit gene were heterozygously deleted at the lesional tissue but not at the normal mucosal tissue. Planar-type GIST of the transverse colon has not been reported yet, and the literature search for the similar cases was done.