Colorectal cancer (CRC)

Definition

CRC is a malignant tumor originating from the epithelial cells lining the large intestine.

CRC is common in developed countries and often occurs due to the transformation of adenomatous polyps. More than half of the cases occur in the rectum and sigmoid colon, and 95% are adenocarcinomas. Colon and rectal cancers are often grouped together (colorectal cancer) because they have so much in common.

Most colorectal cancers start as a growth (polyp) on the inner lining of the colon or rectum.

Polyps vary in types, some can develop into cancer over time.

• Adenomatous polyps (adenomas) are divided into 3 types: tubular, villous and tubulovillous. They can transform into a malignant neoplasm.
• Hyperplastic polyps and inflammatory polyps are more common but generally are not risk factors for CRC. Sessile serrated polyps (SSP) and traditional serrated adenomas (TSA) are similar to adenomas in treatment, as they also have a risk of transforming into CRC.

Regardless of the type of polyp, the risk of developing CRC is increased if:

• polyp is larger than 1 cm,
• more than 3 polyps are detected,
• after polyp removal and pathology examination, the precancerous lesions (dysplasia) are detected.

Most often, CRC occurs in the sigmoid colon and is of glandular origin (adenocarcinoma), the second most common type of adenocarcinoma is adenocarcinoma of the rectum, less often squamous cell carcinoma of the anal canal occurs.

Driver mutations in CRC: