An update on anal neoplasia.

Although anal cancer remains a relatively uncommon tumour its frequency is rising, especially in high-risk groups. It is now well recognized that anal squamous cell carcinoma, the largely predominant tumour type, shares many similarities with cancer of the uterine cervix, with a major role for oncogenic human papilloma viruses in both tumours. Anal squamous precancerous lesions have now to be classified with the same criteria and terminology as their cervical counterparts, by using the Lower Anogenital Squamous Terminology (LAST) proposal. Only p16 protein is a useful marker in this setting at the present time. As most cases of anal cancer are treated by non-surgical procedures, pathology has a limited role in the staging of the disease, except for early lesions treated by local excision, and when the sentinel lymph node procedure is undertaken that is still under evaluation. A variety of other tumour types can occur more rarely, with difficult diagnostic issues, solved in most cases by immunohistochemistry.