Anal cancer: overview, causes, diagnosis and treatment

Types and pathology

The majority of anal cancers are squamous cell carcinoma, which originate in the flat, squamous cells that line the anal canal. Less common histologies include lymphoma, sarcoma and melanoma, each of which follows a different biological behavior and treatment approach.

Risk factors and causes

• Human papillomavirus (HPV) infection—especially oncogenic types—is the primary cause for most squamous anal cancers.
• Behaviors and conditions that increase HPV exposure or reduce immune control: receptive anal intercourse, multiple sexual partners, cigarette smoking, and immunosuppression (for example HIV infection).
• Older age and a history of certain anal or genital lesions are additional risk factors.

Presentation, diagnosis and staging

Common symptoms include rectal bleeding, pain, itching, a palpable lump or changes in bowel habits. Diagnosis relies on a careful physical and digital anal examination, visualization with anoscopy or proctoscopy and biopsy of suspicious lesions. Imaging (CT, MRI, PET) helps define local extent and detect spread. Staging follows the TNM framework used for many solid tumors and guides treatment planning.

Treatment and prognosis

For most squamous anal cancers, combined chemotherapy and radiotherapy is the primary curative approach, preserving the sphincter and avoiding major surgery in many cases. Surgical removal (including more extensive resections) is reserved for small selected tumors, persistent disease after radiation, or distant spread. Advanced disease may require systemic therapies. Prognosis depends strongly on stage at diagnosis; early-stage tumors have substantially better outcomes.

Prevention, screening and public health

HPV vaccination and safe-sex practices reduce risk. Screening strategies focus on high-risk groups and may include clinical exams, anoscopy and cytologic sampling in specialized settings. Although anal cancer is less frequent than colorectal cancer, it causes meaningful morbidity and, in some regions including the United States, several thousand new cases are reported each year. Ongoing research aims to optimize prevention, early detection and treatment.

For more information on general cancer topics, testing and care options consult local specialist services or health resources referenced here: cancer overview, anatomy, colorectal differences, squamous carcinoma details, lymphoma resources, sarcoma information, melanoma guidance, national statistics.