Figure 1.

Colorectal Cancer Progression: From Normal Mucosa to Invasive Carcinoma. This image illustrates the progression of colorectal cancer through the adenoma-carcinoma sequence. It begins with normal mucosa undergoing mutations in tumor suppressor genes, such as APC (5q21) (first hit), followed by epigenetic alterations and silencing of normal alleles (second hit). Over time, proto-oncogene mutations, like K-RAS (12p12), promote uncontrolled growth and the formation of adenomas. If additional mutations accumulate, such as the loss of p53 (17p13) and SMAD2/4 (18q21), along with COX-2 overexpression, the adenoma progresses to an invasive carcinoma with chromosomal alterations and telomerase activation.