Anal Cancer

Anal cancer includes malignancies arising from the anal canal and perianal skin.

Squamous cell carcinoma is by far the commonest histology. Less common tumours include adenocarcinoma and melanoma, which follow different oncological pathways.

Human papillomavirus infection, particularly HPV 16, plays a major role in anal squamous carcinogenesis.

Treatment must therefore begin with histological confirmation rather than treating all anal malignancies as one disease.

Common presentations are:

• Rectal bleeding
• Anal pain
• Anal mass
• Change in bowel habit
• Pruritus
• Nonhealing ulcer
• Inguinal lymphadenopathy

Symptoms are frequently attributed initially to haemorrhoids, causing delayed diagnosis.

Any persistent irregular anal ulcer or mass should be biopsied.

Perform digital rectal examination and anoscopy with biopsy.

Assess both inguinal regions because anal canal cancers drain to inguinal as well as pelvic nodes.

Pelvic MRI: define local tumour and regional nodal disease.

CT chest, abdomen and pelvis or PET CT: stage distant and regional disease.

Tumour histology determines management.

Small well differentiated perianal skin cancers that do not involve the sphincter can occasionally undergo wide local excision with adequate margins.

Most anal canal squamous cancers are treated primarily with definitive chemoradiotherapy rather than radical surgery.

Anal adenocarcinoma is treated more like rectal adenocarcinoma and frequently requires multimodality therapy including radical rectal surgery.

Anal melanoma behaves aggressively and requires specialist melanoma staging and systemic treatment planning.

Do not perform abdominoperineal resection as routine primary treatment for anal squamous cell carcinoma. Radical surgery is primarily reserved for persistent or recurrent disease after chemoradiotherapy.