Squamous cell anal cancer is a type of malignancy that develops in the flat, thin squamous cells lining the anal canal. This cancer typically begins just inside the anal opening. While uncommon, recognizing its characteristics aids early identification.
Understanding Squamous Cell Anal Cancer
Squamous cell carcinoma accounts for approximately 80% of all anal cancers. This cancer is more frequently observed in women, though incidence rates are rising among men. It often affects individuals over the age of 50.
The development of squamous cell anal cancer is linked to several risk factors. Human Papillomavirus (HPV) infection is a primary contributor, especially high-risk strains like HPV-16 and HPV-18, which cause abnormal cell changes. Weakened immune systems, such as from HIV or organ transplants, also increase risk due to reduced ability to clear HPV.
Smoking is another risk factor, as tobacco toxins damage cells. Chronic inflammation, often from anal fistulas, also increases risk. Receptive anal intercourse is associated with elevated risk, likely due to HPV exposure.
Recognizing the Signs
Recognizing the signs of squamous cell anal cancer involves paying attention to persistent changes in the anal area. Common symptoms include bleeding from the anus or rectum, which may appear on toilet paper or in stool and can be mistaken for hemorrhoids.
Pain or discomfort in the anal region, often a persistent ache or pressure, can worsen during bowel movements or prolonged sitting. A palpable lump or tender mass near the anus may also develop.
Changes in bowel habits, such as a persistent urge to have a bowel movement or narrowing of the stool, can also be present. Persistent anal itching, unresponsive to typical treatments, is another symptom. While these symptoms can stem from less serious conditions, they warrant medical evaluation.
Diagnosis and Treatment Approaches
Diagnosis begins with a physical examination, including a digital rectal exam. If concerns arise, an anoscopy may be performed to visualize the anal canal. Suspicious areas prompt a biopsy, where a tissue sample is examined under a microscope to confirm cancer.
Once confirmed, imaging tests stage the cancer, determining its extent and spread. Computed tomography (CT) scans of the abdomen and pelvis identify tumor size and spread. Magnetic resonance imaging (MRI) of the pelvis provides detailed images of the tumor’s relationship to surrounding structures. Positron emission tomography (PET) scans detect cancerous cells throughout the body by identifying areas of increased metabolic activity.
Chemoradiation, combining chemotherapy and radiation therapy concurrently, is the standard treatment for most stages. Chemotherapy drugs, like 5-fluorouracil and mitomycin, enhance cancer cells’ sensitivity to radiation. Radiation therapy targets the tumor with high-energy rays to destroy cancer cells while minimizing damage to healthy tissues. This non-surgical approach aims to preserve anal function and avoid a permanent colostomy.
Surgical options are reserved for specific situations, such as very small, early-stage tumors or cancer that persists or recurs after chemoradiation. Local excision involves surgically removing only the tumor and a small margin of healthy tissue, suitable for superficial, unspread tumors. For more extensive or recurrent disease, an abdominoperineal resection (APR) may be necessary, involving removal of the anus, rectum, and part of the colon, resulting in a permanent colostomy. Following treatment, regular follow-up care, including physical examinations and imaging, monitors for recurrence.
Prevention and Early Detection
Preventive measures and early detection reduce the risk and improve outcomes for squamous cell anal cancer. HPV vaccination is a primary preventive action, protecting against high-risk strains like HPV-16 and HPV-18. The vaccine is recommended for adolescents and young adults, typically before virus exposure.
Practicing safe sexual behaviors also reduces HPV transmission risk. Smoking cessation is another preventive step, as quitting tobacco lowers the risk of various cancers, including anal cancer. Regular medical check-ups, especially for individuals with risk factors like HIV or receptive anal intercourse, allow for early identification of suspicious changes. Early detection improves treatment outcomes, as smaller, localized tumors are more responsive.
References
American Cancer Society. What Is Anal Cancer?. https://www.cancer.org/cancer/types/anal-cancer/about/what-is-anal-cancer.html. Accessed July 27, 2025.
American Cancer Society. Treating Anal Cancer. https://www.cancer.org/cancer/types/anal-cancer/treating.html. Accessed July 27, 2025.
Centers for Disease Control and Prevention. HPV (Human Papillomavirus). https://www.cdc.gov/hpv/index.html. Accessed July 27, 2025.