Superficial depressed-type cancer monitored by colonoscopy through the early phase of invasion.

Although previous retrospective reports have demonstrated the developmental course of several colorectal tumors, the natural history and progression of depressed carcinoma, especially in the early stage, remains obscure. We report a case of superficial depressed tumor in the transverse colon in a 71-year-old man, which did not change in size and gross configuration through prospective colonoscopic observation over a period of 19 months but which was finally diagnosed as early-stage submucosal invasive cancer. Most depressed cancers have been supposed to arise de novo and grow rapidly, showing aggressive behavior when 10 mm or less in size. However, this case report may suggest that even a depressed tumor may grow to approximately 10 mm within the mucosal layer over a few years and that the growth of colorectal tumors, whether they are polypoid or depressed in configuration, might be fairly slow.