PRECURSOR LESIONS OF COLORECTAL CANCERS

Abstract

Adenoma is recognized as a precursor lesion of colorectal cancer in the traditional colorectal carcinogenesis theory, the adenoma-carcinoma sequence. Another colorectal carcinogenesis theory, the so-called serrated pathway, was recently proposed, and traditional serrated adenoma (TSA) and sessile serrated adenoma/polyp (SSA/P) have been additionally recognized as precursor lesions of colorectal cancer. The cancer component in adenoma, TSA and SSA/P has been reported to account for approximately 10%. This indicates that the malignant potential of the three precursor lesions is equivalent. Hamartomatous polyps, including Peutz-Jeghers syndrome and juvenile polyposis, also have the potential to develop into carcinoma lesions, although at a relatively low incidence. Dysplasia occurs on the longstanding inflammatory background mucosa in cases of ulcerative colitis (dysplasia-carcinoma sequence). Aberrant crypt foci are clusters of abnormal crypts which can be visualized using a stereoscopic microscope or magnifying endscope after staining the mucosal surface with methylene blue. It has been suggested that ACF are the earliest detectable precancerous lesions of colorectal cancer. However, it still remains controversial whether ACF actually develop into a polyp and carcinoma eventually.