MALIGNANT ANAL TUMORS

Anal rumours represent 5 per cent of anorectal cancers and exist as tw o clinical entities: tumours of the anal canal and those of the anal m argin. Smoking and sexual behaviour, particularly homosexual anal inte rcourse, are important aetiological factors. This association is relat ed to anal warts and human papillomavirus infection, notably type 16, which is found in around 70 per cent of warts. Symptoms are non-specif ic and are frequently attributed to benign conditions. Rectal examinat ion reveals a characteristically infiltrating lesion and any suspiciou s anal area should be biopsied. There are two histological types. Squa mous carcinoma comprises approximately 95 per cent of anal tumours and includes the 35 per cent of tumours derived from the anal transition zone (cloacogenic tumours), containing a mixture of squamous and mucin ous elements. The remaining 5 per cent of anal tumours are adenocarcin oma. Squamous cell rumours of the anal canal are probably best treated using radiotherapy (with chemotherapy) as complete response rates, 5- year survival rates, and incidences of normal sphincter function and s ignificant toxicity are around 80, 70, 75 and 20 per cent respectively . Treatment failures may be salvaged by surgery. The 5-year survival a nd local recurrence rates for radical surgery are around 60 and 25 per cent respectively; there are few indications for local excision. In c ontrast, 60 per cent of anal margin rumours are suitable for local exc ision, the 5-year survival rate being in excess of 80 per cent. Combin ing radiotherapy with surgery may give additional benefit. Current ran domized controlled trials should further clarify the relative merits a nd demerits of the treatment options.