High-grade colon dysplasia is a type of colon cancer that is still in situ, according to Johns Hopkins Medicine. It has penetrated the inner layers or mucosa of the large intestine, but it has not penetrated to deeper muscle layers.
This type of cancer is in its earliest stage, according to the American Cancer Society. If it is treated promptly, the survival rates are very high; the survival rate of high-grade colon dysplasia is not even listed in the ACS Surveillance, Epidemiology and End Results database. It begins with Stage 1 cancer, whose 5 year survival rate is 92 percent. High-grade colon dysplasia is a Stage 0 cancer.