Potato, po-tah-to? Though they occur in nearby areas of the body, anal cancer and colorectal cancer are two distinct diseases with different causes, risk factors, symptoms, and treatment approaches. Understanding the difference between them can help with early detection and better outcomes. This is a very basic overview meant to answer general medical questions. This is not medical advice! If you come see me in the office (and I hope you never do), we go way more in-depth about treatment options.
– Colorectal cancer starts in the colon or rectum—the large intestine responsible for absorbing water and forming stool.
– Anal cancer develops in the anal canal, the short passage at the end of the rectum through which stool exits the body.
While they’re close anatomically, they arise from different types of cells and often behave very differently. Colorectal cancer tends to be glandular cells from the inside of the colon (adenocarcinoma) and anal cancer tends to be skin cells from outside the anus (squamous cell carcinoma). Of course, for every definition, there is something that defies definition, so there are rare anal canal glandular cancers— best to leave that to pathologists to sort out.
– Colorectal cancer is commonly linked to lifestyle factors, family history, and age. Risk increases with diets high in red or processed meat, obesity, smoking, and lack of physical activity.
Anal cancer, on the other hand, is strongly associated with human papillomavirus (HPV) infection—particularly high-risk strains like HPV-16.
Colorectal cancer often causes:
– Changes in bowel habits (diarrhea, constipation)
– Blood in the stool
– Abdominal pain or bloating
– Unexplained weight loss
Anal cancer may present with:
– Rectal bleeding
– Pain or pressure in the anal area
– A lump or mass near the anus
– Itching or discharge
Both cancers can cause rectal bleeding, which is why proper diagnosis is essential.
Colorectal cancer has established screening guidelines starting at age 45 with colonoscopy or stool-based tests like FIT or Cologuard.
Anal cancer does not have universal screening guidelines, but anal Pap smears and high-resolution anoscopy may be recommended for high-risk individuals (e.g., people with HIV, men who have sex with men, and women with a history of cervical dysplasia).
Colorectal cancer is typically treated with a combination of surgery, chemotherapy, and sometimes radiation, depending on stage.
Anal cancer is often treated with chemoradiation (combined chemotherapy and radiation), avoiding surgery unless the cancer is resistant or recurrent.
While anal cancer and colorectal cancer may seem similar, they are very different in origin and management. Knowing your risk factors and recognizing symptoms early can lead to faster diagnosis and better outcomes.
When in doubt, get it checked out. Early detection saves lives—no matter where the cancer starts.
Until next time, that’s just the way the anus wrinkles.
