Carcinoma of colon (Robbins pp 833)

Epidemiology: Peak incidence between 60-79yrs. Most common in USA and other developed nations, and least common in developing nations.

Aetiology: dietary (i.e.: obesity, low fibre, high refined carbohydrates, red meat, low vitamins ACE) is the main factor. Low fibre means increased faecal transit time  altered bacterial flora of intestine ≫ toxic byproducts of carbohydrate degradation by bacteria are making longer contact with colonic mucosa. Intestinal bacteria also convert bile acids ≫ carcinogens. Other factors include: colonic disease (i.e.: adenomas, ulcerative colitis).

Macroscopic appearance of colon cancer: Most cancers occur distally (sigmoid, rectum). Proximal lesions are usually exophytic, polypoid in nature. Distal lesions are annular, fungating (cauliflower) and have central ulcerative part. Both types eventually go through the wall of colon, and past serosa.

Microscopic appearance of colon cancer: adenocarcinoma (glandular structure) with mucus producing cells.

Spread: local lymph nodes along mesentery, central abdominal lymph nodes, eventually into venous system ≫ liver, brain, lungs. Can spread distally into lymph nodes serving the bladder, pelvis.

Staging of colon cancer: Dukes criteria of staging. A – mucosa, B1 – extends to muscle layer, B2 – penetrates muscle layer, C1 – extends to muscle layer + lymph node involvement, C2 – penetrates muscle layer + lymph node involvement, D – metastases.

Clinical features: Right sided tumours: fatigue, weakness, iron def anaemia (all 2^nd to bleeding), Left sided tumours: left lower quadrant pain, diarrhea, constipation, occult bleeding. Rectal bleeding is carcinoma until proven otherwise.

Category: Pathology Notes