| [ Summary ] |
In Japan, depressed colorectal cancers, which develop via the de novo pathway, are one of the leading causes for the development of colorectal cancers. However, there are not reports on the occurrence of depressed colorectal cancer in Western countries. In the 1990's, some young Japanese endoscopists visited Western countries, and they reported the existence of depressed colorectal cancers in Western populations. Thereafter, foreign endoscopists who learned about the Japanese techniques for endoscopic diagnosis have conducted high-quality research on the status of depressed colorectal cancers in Western countries. International consensus meetings on "the Paris endoscopic classification of superficial neoplastic lesions" and "nonpolypoid neoplastic lesions of the colorectal mucosa" have been held, and their findings have been published in the supplements of Gastrointestinal Endoscopy. In future studies, further evidence regarding the molecular mutations in de novo cancer is required to understand the important pathways involved in colorectal carcinogenesis. |