Types of Colon Cancer

"Colon cancer" covers several types by cell origin and tumor biology. Nearly all are one type - but the biology increasingly guides treatment, so the names are worth knowing.

Adenocarcinoma (over 95%)

The standard colon cancer, arising from the mucus-making gland cells of the colon lining. Everything about polyps, screening and staging applies to this type. Variants include mucinous and signet-ring cell adenocarcinomas - the latter rarer and more aggressive.

By location

• Right-sided (cecum, ascending colon): tend to grow flatter, bleed silently - found via anemia
• Left-sided (descending, sigmoid): narrow the passage - changed habits and visible blood earlier
• Rectal cancer: anatomically distinct management (radiation often added) though biologically a cousin - together with colon cancer it forms "colorectal cancer"

By molecular type (what the lab reports mean)

• MSI-high / dMMR tumors: about 15% - these respond remarkably well to immunotherapy; testing is now routine
• KRAS/NRAS and BRAF mutations: guide whether targeted antibody drugs will work in advanced disease
• HER2 amplification: a small subgroup with its own targeted options
• These tests turn "colon cancer" into a personalized treatment map - ask what the tumor's markers showed

Rarer types

• Neuroendocrine tumors, lymphomas, GISTs and sarcomas of the colon: uncommon, differently behaved, differently treated
• Hereditary syndromes (Lynch, FAP): not a cell type but a family pattern - identification changes screening for the entire family

One-line summary

Almost all colon cancers are adenocarcinomas, sorted by location and molecular markers (MSI, KRAS, BRAF, HER2) that now steer treatment - with rarer cell types and hereditary syndromes as important exceptions.