Squamous Cell Carcinoma of the Anal Canal
Synonyms
SCAC, anal canal squamous cell carcinoma, epidermoid carcinoma of the anus, anal squamous cell carcinoma,Overview
Squamous Cell Carcinoma (SCC) of the anal canal is a rare, increasing malignancy (2–4% of gastrointestinal cancers) often linked to HPV and HIV, predominantly affecting the squamous epithelium. Common symptoms include anal bleeding, pain, and, in some cases, a palpable mass. Standard treatment involves sphincter-preserving combined chemoradiation (Nigro protocol) rather than upfront surgery.
Symptoms
Symptoms of Squamous Cell Carcinoma (SCC) of the anal canal often mimic less serious conditions like hemorrhoids, causing delayed diagnosis. Key symptoms include rectal bleeding, persistent pain, itching, a lump near the anus, and changes in bowel habits. Early detection is crucial, as early-stage SCC is often curable.
Causes
Squamous Cell Carcinoma (SCC) of the anal canal is primarily caused by persistent, high-risk Human Papillomavirus (HPV) infection, responsible for over 90% of cases. Key risk factors include HIV/AIDS, smoking, weakened immunity, and anal receptive intercourse. It is most common in individuals over 50.
Prevention
Squamous Cell Carcinoma of the Anal Canal (ASCC) is primarily prevented by reducing exposure to high-risk HPV through vaccination (Gardasil 9) for individuals aged 9–45 and practicing safe sex. High-risk groups, including people with HIV or a history of anal/cervical warts, should receive regular anal cancer screenings (anoscopy) to detect and treat precancerous lesions (HSIL) early.
Diagnosis
Squamous Cell Carcinoma (SCC) of the anal canal is diagnosed primarily through a digital rectal exam (DRE), high-resolution anoscopy (HRA), and confirmed by a tissue biopsy. Symptoms often include anal bleeding, pain, a lump, or itching, which are frequently mistaken for hemorrhoids. Imaging tests like MRI, CT, or PET scans are used to determine the stage.
Prognosis
Squamous Cell Carcinoma (SCC) of the anal canal has a generally favorable prognosis, with a
5-year survival rate of approximately 70%–80%. Primary treatment with chemoradiation is highly effective, often avoiding the need for surgery. Prognosis is closely tied to stage, with early-stage (Stage I) 5-year survival at 71.3%. Women, younger patients, and those with localized disease tend to have better outcomes.
Treatment
Squamous Cell Carcinoma of the Anal Canal (ASCC) is primarily treated with definitive concurrent chemoradiation (CRT), which avoids permanent colostomy in most cases. The standard regimen combines radiation with 5-fluorouracil (5-FU) and mitomycin. For early, small tumors (T1N0), local excision may be used, while advanced, recurrent, or metastatic cases may require salvage abdominoperineal resection (APR) or immunotherapy.