Description
Anal cancer is a malignant tumor arising from the tissues of the anal canal or perianal skin. The anal canal is the short terminal segment of the gastrointestinal tract, extending from the rectum to the anus, and plays a key role in bowel continence.
Although anal cancer is relatively rare compared with colorectal cancer, its incidence has been increasing globally, particularly due to chronic infection with human papillomavirus (HPV). Most anal cancers are slow-growing and, when detected early, are highly treatable with non-surgical therapies.
Types
Anal cancer is classified based on the cell of origin:
Squamous Cell Carcinoma (SCC)
Most common type (≈85–90%)
Arises from squamous epithelium of the anal canal
Strongly associated with HPV infection (especially HPV-16)
Highly sensitive to chemoradiotherapy
Adenocarcinoma
Originates from glandular cells
Less common
Often managed similarly to rectal cancer
Basal Cell Carcinoma
Rare
Usually slow growing
More common in perianal skin
Melanoma (Anal Melanoma)
Very rare but aggressive
Often diagnosed late
Poor prognosis
Neuroendocrine Tumors / Sarcomas
Extremely rare
Require specialized management
Stages
Anal cancer is staged using the TNM system, mainly based on tumor size and spread:
Stage 0 (Carcinoma in situ)
Abnormal cells confined to surface epithelium
Stage I
Tumor ≤2 cm
No lymph node or distant spread
Stage II
Tumor >2 cm
Still confined locally
Stage III
Spread to regional lymph nodes (inguinal, pelvic)
Stage IV
Distant metastasis (liver, lungs, bone)
Tumor size is more important than depth of invasion in anal cancer staging.
Risk Factors
Major risk factors include:
HPV infection (most significant)
History of anal warts
Multiple sexual partners
Receptive anal intercourse
HIV infection / immunosuppression
Smoking
Chronic inflammation of the anal region
Older age (most cases >50 years)
History of cervical, vulvar, or vaginal cancer
Symptoms
Symptoms are often mistaken for hemorrhoids, causing delayed diagnosis:
Rectal bleeding (most common)
Anal pain or discomfort
Sensation of a lump or mass
Itching or discharge
Changes in bowel habits
Tenesmus (feeling of incomplete evacuation)
Enlarged groin lymph nodes
Advanced cases: weight loss, fatigue
Persistent anal bleeding should always be investigated.
Diagnosis
Diagnosis involves a combination of clinical, endoscopic, and imaging assessments:
Clinical Examination
Digital rectal examination (DRE)
Inspection of perianal region
Endoscopy
Anoscopy / Proctoscopy
Biopsy (gold standard)
Imaging
MRI pelvis → local tumor staging
CT chest/abdomen/pelvis → metastasis
PET-CT → lymph node involvement
Laboratory Tests
HIV testing
HPV-related assessment (supportive, not diagnostic)
Facts (FAQ)｜常见问题
Q1: Is anal cancer the same as colorectal cancer?
No. Anal cancer differs in biology, staging, and treatment, and responds better to chemoradiotherapy.
Q2: Can hemorrhoids turn into anal cancer?
No, but symptoms may overlap. Persistent symptoms must be evaluated.
Q3: Is HPV always present in anal cancer?
Most cases are HPV-related, but not all.
Q4: Does anal cancer always require surgery?
No. Most patients are cured without surgery.
Q5: Can anal cancer be cured?
Yes. Especially when detected early.
Prostate cancer
Endometrial Cancer
Tongue Cancer
*Disclaimer: The effect of treatment varies from person to person. The information on the website of Modern Cancer Hospital Guangzhou is for reference only, and cannot be used as the basis for medical diagnosis and treatment, nor can it replace the doctor's diagnosis and treatment. For more details, please review the Liability Clause.
