Anal cancer accounts for an estimated 8590 cases and about 1350 deaths in the US annually (1). The main symptom is bleeding with defecation. Diagnosis is by endoscopy. Treatment options include excision and chemotherapy and radiation therapy.
Squamous cell carcinoma (nonkeratinizing squamous cell or basaloid carcinoma) of the anorectum accounts for 3 to 5% of distal large-bowel cancers. Basal cell carcinoma, Bowen disease (intraepidermal squamous cell carcinoma), extramammary Paget disease, cloacogenic carcinoma, and malignant melanoma are less common. 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:
- Human papillomavirus (HPV) infection
- Chronic fistulas
- Irradiated anal skin
- Lymphogranuloma venereum infection
- Condyloma acuminatum infection
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 HIV-infected patients (see Squamous cell cancer of the anus and vulva). Higher grades may progress to invasive carcinoma. It is unclear whether early recognition and eradication improve long-term outcome; hence, screening recommendations are unclear.
- 1. Siegel RL, Miller KD, Jemal A: Cancer statistics, 2020. CA Cancer J Clin 70(1):7–30, 2020. doi: 10.3322/caac.21590
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. A mass may be palpable on digital rectal examination.
Diagnosis of Anal Cancer
- Sigmoidoscopy or colonoscopy
- Sometimes biopsy
A flexible sigmoidoscopy or rigid anoscopy or sigmoidoscopy is done to evaluate the area. 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.
Staging by CT, MRI, or positron emission tomography (PET) is advisable.
Treatment of Anal Cancer
- Combination chemotherapy and radiation therapy
- Sometimes surgical resection
Combination chemotherapy and radiation therapy is the initial therapy in most cases and results in a high rate of cure when used for anal squamous and cloacogenic tumors.
Abdominoperineal resection is indicated when radiation and chemotherapy do not result in complete regression of the tumor or there is recurrent disease.