Anal Cancer Symptoms and Why They're Often Missed

NCI's anal cancer symptom page is short. It names five things and says each may be caused by anal cancer or by other conditions.

• Bleeding from the anus or rectum
• A lump near the anus
• Pain or pressure in the area around the anus
• Itching or discharge from the anus
• A change in bowel habits

That list is the whole list. Nothing on it is unique to cancer. Hemorrhoids, which are swollen veins around the anus, and anal fissures, which are small tears in the lining, produce the same complaints far more often.

NCI's PDQ summary for health professionals adds something the symptom page does not. Lymph drainage from the anus follows the inguinal vein, which runs toward the groin. PDQ says the first evaluation includes a careful exam of the groin. Any lymph node that can be felt gets a biopsy.

So a swollen groin node is not a symptom people are told to watch for, but it is something a clinician will deliberately check.

PDQ names only two major prognostic factors for anal cancer: tumor size and node status. It says primary tumors smaller than 2 cm carry a better prognosis.

Those centimeters run straight through the staging tables. In the AJCC system PDQ reprints, T1 is a tumor 2 cm or smaller. T2 is larger than 2 cm and up to 5 cm. T3 is larger than 5 cm. T4 is any size that has invaded a neighboring organ such as the vagina, urethra, or bladder.

A delay is not an abstract risk. It is the difference between one line of that table and the next.

PDQ states that anal cancer is usually curable. The figures behind that sentence are worth reading carefully.

Most patients arrive with T1 or T2 disease, meaning 5 cm or smaller. Fewer than 20% have cancer in lymph nodes. For those early-stage patients, PDQ puts 5-year survival above 85%.

Even with node-positive disease, PDQ says 5-year survival exceeds 50%, provided the cancer has not invaded adjacent organs or spread to distant sites.

Read together, those two facts explain why the awkwardness of the exam is a poor trade. The prognosis is good, and it is best when the tumor is small.

The American Cancer Society projects 11,270 new cases of anal, anal canal, and anorectal cancer for 2026, and 1,700 deaths. SEER Stat Facts carries that projection. That is uncommon next to breast, lung, or colorectal cancer.

But PDQ says the risk is rising, and it names the reason. More human papillomavirus infection. It states that 95% of anal cancers are HPV related. Serotypes 16 and 18 carry the highest risk. Pathologists can tie HPV involvement to P16 staining on the tissue.

PDQ adds that people with HIV have a higher rate of HPV coinfection and, as a result, a higher risk of anal cancer. It also notes data linking risk to receptive anal intercourse and to a high lifetime number of partners. PDQ frames these as routes to HPV exposure, not as causes on their own.

That link makes the virus worth reading about on its own. Prevention and symptom-checking are separate conversations.

Most primary anal cancers are squamous cell carcinomas. Another name for them is epidermoid carcinomas. PDQ notes that some tumors from the transitional zone were once labeled cloacogenic or basaloid. Those are now counted as nonkeratinizing squamous cell cancers. They are tied to HPV in the same way.

Location changes the label. PDQ defines the anal canal as running from the rectum to the perianal skin, lined by mucous membrane over the internal sphincter. Lesions in hair-bearing skin beyond the squamous mucocutaneous junction are called perianal cancers. PDQ says these are typically treated the same way, though local treatment alone can be considered for a discrete skin lesion well separated from the anal verge.

Two things sit outside this picture. Adenocarcinomas that start in anal glands or in a fistula are rare. PDQ says they behave more like rectal adenocarcinoma. Anal melanoma is not covered by this summary at all.

The N categories in the anal system are geographic. PDQ's tables define N1 as spread to inguinal, mesorectal, internal iliac, or external iliac nodes. N1a covers inguinal, mesorectal, or internal iliac nodes. N1b covers external iliac nodes. N1c covers external iliac nodes together with any N1a node.

Stage 0 sits apart from all of it. PDQ defines Tis as high-grade squamous intraepithelial lesion. That label replaced several older ones: carcinoma in situ, Bowen disease, and anal intraepithelial neoplasia grade II to III.

PDQ's treatment table is short enough to read in one pass. Stage 0 is treated with surgery. Stages I, II, and III are treated with local resection, or external-beam radiation combined with chemotherapy, or alternative strategies, or radical resection. Stage IV is handled with palliative surgery, palliative radiation, palliative chemotherapy with or without radiation, or checkpoint inhibitors.

PDQ says the best approach for advanced disease is still under clinical evaluation. That is a plain statement of an open question, not a hedge.

There is no NCI-published waiting period after which a symptom becomes urgent. The instruction on the symptom page is simply to check with a doctor about any of the five findings.

Three things can be said without inventing a threshold. These symptoms overlap almost fully with common harmless conditions. The exam that tells them apart is quick. And the staging tables reward finding a tumor while it is under 2 cm. A symptom that is not clearing with usual hemorrhoid care is worth a look, rather than another month of ointment.

Clinicians examine this region routinely. Bleeding, lumps, itching, and changes in bowel habits are ordinary reasons for an appointment, not unusual ones.

The disease as a whole is described in anal cancer. How the T and N categories combine into stages is covered in anal cancer stages. The virus behind 95% of these cancers is explained in HPV and cancer.

• NCI: anal cancer symptoms
• NCI PDQ: anal cancer, HP version
• SEER Stat Facts: anal cancer (2026 case and death projections from the American Cancer Society)