Anal cancer is an uncommon malignancy that starts in the anus — the opening at the end of the rectum.

The American Society of Clinical Oncology estimates that 8,300 cases of anal cancer will be diagnosed in 2019 and about 1,280 deaths will occur that year from anal cancer.

By contrast, some 140,250 people are predicted to be diagnosed with colorectal cancer in the U.S. in 2019, and about 51,000 people are predicted to die of the disease the same year.

Approximately half of all anal cancers are diagnosed before the malignancy has spread beyond the primary site, whereas 13% to 25% are diagnosed after the cancer has spread to the lymph nodes, and 10% are diagnosed after the cancer has spread to distant organs, or has metastasized.

When it is found early, anal cancer is highly treatable.

The overall five-year survival rate following diagnosis of anal cancer is 67%.

The cancer may also be detected with more invasive procedures such as an anoscopy, proctoscopy, or endorectal ultrasound.

If cancer is suspected, a biopsy should be done and the specimen examined by a pathologist.

Staging workup may include an abdominal and pelvic CT scan, a pelvic MRI scan to assess the pelvic lymph nodes, a chest x-ray, and liver function studies. PET scans are sometimes performed.