Colorectal cancer

What it is

The commonest histological type for colon cancer is adenocarcinoma. On colonoscopy the lesion is described as circumferential, ulcerating and fungating.

Causes and risk

Individuals at higher risk are those with a personal history of adenomatous polyps, colorectal cancer, inflammatory bowel disease or a genetic cancer syndrome, or a family history of adenomatous polyps or colorectal cancer. Familial adenomatous polyposis is the far end of that range:

• Autosomal dominant mutations of the APC gene, a tumor suppressor gene on chromosome 5q22, with 20 to 25% of cases having a negative family history
• Polyposis typically develops within the second or third decade of life
• Polyps develop in the entire colon, always including the rectum, and more than 100 polyps are typically detected in the classic form
• The lifetime risk of colorectal cancer is 100% by 45 years of age

Diverticular disease can also end in colorectal cancer, and in colo-vesical fistula with pneumaturia, feces in urine and recurrent UTI. Set out as a list, the risk factors divide in two. Modifiable: low fiber diet, high red meat diet, obesity, sedentary lifestyle, smoking and alcohol. Non modifiable: age, male gender, family history, and genetic conditions like FAP and Lynch syndrome. The screening list adds aging over 40, a family history of colorectal cancer, familial adenomatous polyposis, Peutz-Jeghers syndrome, juvenile polyposis syndrome or hereditary nonpolyposis colorectal cancer, a past history of colorectal adenomas, serrated polyps or inflammatory bowel disease, and radiation.