Anal cancer accounts for an estimated 9760 cases and about 1870 deaths in the United States 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) is the most common cause 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. 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:
Chronic fistulas
Irradiated anal skin
Lymphogranuloma venereum infection
Condyloma acuminatum infection
Smoking
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. It is unclear whether early recognition and eradication improve long-term outcome; hence, screening recommendations are unclear.
General reference
1. Siegel RL, Miller KD, Wagle NS, Jemal A: Cancer statistics, 2023. CA Cancer J Clin 73(1):17–48, 2023. doi: 10.3322/caac.21763
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
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.
Once anal cancer is diagnosed, staging by CT of the chest, abdomen, and pelvis; MRI; or positron emission tomography (PET) is required to rule out metastatic disease.
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 anal squamous and cloacogenic tumors.
Tumor regression continues for up to 6 months after completion of chemoradiation (1). 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 reference
1. James RD, Glynne-Jones R, Meadows HM, et alLancet Oncol 14(6):516–524, 2013. doi: 10.1016/S1470-2045(13)70086-X
