There have been no reports of Cronkhite–Canada syndrome (CCS) associated gastric cancer resected with endoscopy because it is very difficult to identify small cancers that are candidates for endoscopic resection. We report a case of CCS with gastric cancer treated with endoscopic submucosal dissection, and we evaluate the molecular pathological analysis of malignant transformation in patients with CCS. A 74-year-old man had an advanced rectal cancer and gastrointestinal polyposis after presenting with hypoproteinemia, partial hair loss and atrophic nails as well as hyperpigmentation on the hands. He was diagnosed as having CCS. On upper endoscopy, a 7 mm discolored polyp with an irregular microvascular pattern revealed by magnified narrow-band imaging (NBI) was identified in gastric diffuse CCS polyposis. This lesion was treated with endoscopic submucosal dissection and diagnosed as a flat, elevated-type, mucosal well-differentiated tubular adenocarcinoma without lymphatic or venous infiltration, and with tumor-free margins. Microsatellite instability was detected in both the cancer and the surrounding CCS polyps. Mucin-histochemical analysis of the cancer area showed the complete intestinal type, and thus may have differentiated the CCS polyps from that of the common gastric hyperplastic polyps. This case illustrates that a clue to detecting small cancers may be to look for the discolored lesion among reddish CCS polyposis and thereafter to observe the irregular vascular pattern with NBI endoscopy. From the viewpoint of genetic alterations, patients with CCS polyps are considered to be at high risk for developing gastric cancer, and therefore careful follow-up examinations are necessary for the early detection of malignancies.
