Pathology of colorectal cancer

The rectum is generally the most common site, accounting for about 3/5 of colorectal cancers, and decreases gradually as it goes upwards, and increases again in the cecum.

Gross classification

(1) Early colorectal cancer: flat type: mostly intramucosal cancer; polyp-shaped type: mostly intramucosal cancer; flat-shaped type: mostly involving the submucosal layer; flat-shaped type: involving the submucosal layer.

(2) Mid- to late-stage colorectal cancer: mass-type: better prognosis; ulcer-type: poorer prognosis; invasive-type: poorer prognosis.

Histological classification

(1) Adenocarcinoma: accounts for nearly 4/5 of colorectal cancer.

(2) Mucinous carcinoma: about 1/5.

(3) Undifferentiated carcinoma: about 2%.

(4) Others: squamous cell carcinoma, squamous adenocarcinoma, small cell carcinoma, etc. are all rare.