- Anal Cancer
- Benign Esophageal Tumors
- Colorectal Cancer
- Colorectal Cancer Screening
- Esophageal Cancer
- Familial Adenomatous Polyposis
- Gastrointestinal Stromal Tumors (GISTs)
- Lynch Syndrome
- MUTYH Polyposis Syndrome
- Pancreatic Cancer
- Peutz-Jeghers Syndrome
- Polyps of the Colon and Rectum
- Small-Bowel Tumors
- Stomach Cancer
Topic Resources
Anal cancer accounts for an estimated 10,540 cases and approximately 2,190 deaths in the United States annually (1).
Squamous cell carcinoma (nonkeratinizing squamous cell or basaloid carcinoma) is the most common histologic form of cancer of the anorectum. Basal cell carcinoma, Bowen disease (intraepidermal squamous cell carcinoma), extramammary Paget disease, cloacogenic carcinoma, and malignant melanoma are less common types of anal cancer. Other tumors include lymphoma and various sarcomas. Metastasis occurs along the lymphatics of the rectum and into the inguinal lymph nodes.
Risk factors for anal cancer include the following:
Anal-receptive intercourse
Chronic fistulas
Irradiated anal skin
Lymphogranuloma venereum infection
Condyloma acuminatum infection
Smoking
HPV infection is the most common risk factor for anal cancer, particularly HPV serotypes 16 and 18, accounting for over 80% of cases (2). People having receptive anal intercourse are at increased risk. Patients with HPV infection may manifest dysplasia in slightly abnormal or normal-appearing anal epithelium (anal intraepithelial neoplasia—histologically graded I, II, or III).These changes are more common among patients with HIV infection (see Squamous cell cancer of the anus and vulva). Higher grades may progress to invasive carcinoma. The randomized ANCHOR study demonstrated that eradication of high-grade squamous intraepithelial lesions decreased the rate of progression to future anal cancer by 57%. Although screening in high-risk individuals (largely HIV positive) has been supported by the U.S. Department of Health as a result of this study, screening has not yet been formally adopted into various societal guidelines (eg, the National Clinical Practice Guidelines in Oncology [NCCN], the American Society of Colon and Rectal Surgeons [ASCRS]) but can be considered (3).
References
1. Siegel RL, Giaquinto AN, Jemal A. Cancer statistics, 2024 [published correction appears in CA Cancer J Clin. 2024 Mar-Apr;74(2):203. doi: 10.3322/caac.21830]. CA Cancer J Clin. 2024;74(1):12-49. doi:10.3322/caac.21820
2. Lin C, Franceschi S, Clifford GM. Human papillomavirus types from infection to cancer in the anus, according to sex and HIV status: a systematic review and meta-analysis. Lancet Infect Dis. 2018 Feb;18(2):198-206. doi: 10.1016/S1473-3099(17)30653-9
3. Palefsky JM, Lee JY, Jay N, et al. Treatment of Anal High-Grade Squamous Intraepithelial Lesions to Prevent Anal Cancer. N Engl J Med. 2022;386(24):2273-2282. doi:10.1056/NEJMoa2201048
Symptoms and Signs of Anal Cancer
Bleeding with defecation is the most common initial symptom of anal cancer. Some patients have pain, tenesmus, or a sensation of incomplete evacuation; others have no symptoms. A mass may be palpable on digital rectal examination.
Diagnosis of Anal Cancer
Rigid anoscopy
Biopsy
A rigid anoscopy is performed to evaluate the area (1). Flexible sigmoidoscopy, rigid proctoscopy, or colonoscopy may be performed if there are other symptoms concerning for colorectal cancer (eg, changes in bowel function, abdominal distention) or if disease extends proximally into the rectum and cannot be fully visualized by anoscopy alone. Skin biopsy by a dermatologist or surgeon might be needed for lesions near the squamocolumnar junction (Z line). Whenever rectal bleeding occurs, even in patients with obvious hemorrhoids or known diverticular disease, coexisting cancer must be ruled out.
Once anal cancer is diagnosed, staging by CT of the chest, abdomen, and pelvis; MRI; or positron emission tomography (PET) is required to exclude metastatic disease.
Diagnosis reference
1. Benson AB, Venook AP, Al-Hawary MM, et al. Anal Carcinoma, Version 2.2023, NCCN Clinical Practice Guidelines in Oncology. J Natl Compr Canc Netw. 2023 Jun;21(6):653-677. doi: 10.6004/jnccn.2023.0030
Treatment of Anal Cancer
Combination chemotherapy and radiation therapy (chemoradiation)
Sometimes surgical resection for treatment of refractory disease or recurrence
Chemoradiation is the initial therapy in most cases and results in a high rate of cure when used for squamous cell carcinomas causing anal cancer (1).
Tumor regression continues for up to 6 months after completion of chemoradiation (2). Observation for a complete response during this time period is acceptable before considering surgery.
Abdominoperineal resection is indicated when radiation and chemotherapy do not result in complete regression of the tumor or there is recurrent disease.
Treatment references
1. Benson AB, Venook AP, Al-Hawary MM, et al. Anal Carcinoma, Version 2.2023, NCCN Clinical Practice Guidelines in Oncology. J Natl Compr Canc Netw. 2023 Jun;21(6):653-677. doi: 10.6004/jnccn.2023.0030
2. James RD, Glynne-Jones R, Meadows HM, et al. Mitomycin or cisplatin chemoradiation with or without maintenance chemotherapy for treatment of squamous-cell carcinoma of the anus (ACT II): A randomised, phase 3, open-label, 2 × 2 factorial trial. . Mitomycin or cisplatin chemoradiation with or without maintenance chemotherapy for treatment of squamous-cell carcinoma of the anus (ACT II): A randomised, phase 3, open-label, 2 × 2 factorial trial.Lancet Oncol. 14(6):516–524, 2013. doi: 10.1016/S1470-2045(13)70086-X
Drugs Mentioned In This Article
