Anorectal Tumors

Cancer may develop in the perianal skin, the anal canal, or the lower rectum. Epidermoid carcinoma accounts for 2% of colorectal cancers and 90% of anal cancers. The histologic types of anal carcinoma include squamous cell, basal cell, basaloid squamous, and cloacogenic carcinomas. Other malignant tumors include Bowen's disease (intraepithelial squamous cell carcinoma in situ), extramammary Paget's disease, carcinoid tumor, and malignant melanoma. Cloacogenic carcinoma is most prevalent in patients aged 60 to 70. Predisposing factors include human papillomavirus types 16 and 18 or HIV infection, leukoplakia, lymphogranuloma venereum, chronic fistula formation, irradiation of the anal skin, and organ transplantation. The disease spreads by direct extension into soft tissues with early lymphatic dissemination.

Symptoms, Signs, and Diagnosis

Bleeding is the most common symptom. Other common complaints are anal discomfort, constipation, and diminished stool caliber. The presenting feature may be a mass on digital rectal examination, inguinal adenopathy, or perianal dermatitis. Cancer should be considered with all nonhealing ulcers or fistulas, and a biopsy must be obtained.

Treatment

The treatment of choice is local surgical excision. A course of radiation therapy and chemotherapy may be needed to debulk a large tumor mass before surgery. Such radiation therapy and chemotherapy may obviate abdominoperineal resection in many patients. Favorable cancers of the lower rectum can be treated with procedures other than proctectomy (eg, local excision, intracavitary radiation therapy, and electrocoagulation). In cases of carcinoma of the anal canal, remarkable local tumor control with chemoradiation therapy has been demonstrated.

Local excision is satisfactory for polypoid rectal tumors that are not fixed, not > 2 cm in diameter, and of low or moderate differentiation.

Fulguration with electrocautery and laser photocoagulation are palliative measures used for selected patients.