Morphology of anal carcinoma: a reappraisal

Properties of HPV-positive and HPV-negative anal carcinomas

Evidence of human papillomavirus (HPV) can be found in up to 85 per cent of anal carcinomas. In the vulva, a discrete subset of HPV-positive carcinomas which show koilocytic morphology and distinct clinical features has recently been identified (warty carcinoma). The morphological and prognostic features of HPV-positive and HPV-negative anal carcinomas were compared in this study of the tumour distribution of HPV DNA. Vulval and anal neoplasia are similar in many ways and we have also looked to see if their similarity extends to 'warty' morphology in relation to HPV status. Thirty-five resection specimens of anal carcinoma were examined with biotin-labelled probes for HPV 6, 11, 16, and 18 DNA, using a non-isotopic in situ hybridization (ISH) technique. No tumour was found to contain HPV 6, 11, or 18. Twenty-four (72 per cent) showed positivity for HPV 16 DNA. Staining was homogeneous and independent of local squamous, basaloid, or ductal differentiation. The majority of tumours showed staining suggestive of episomal, non-productive HPV infection. HPV-positive tumours were more likely to occur in the anal canal than perianally and to show a mixed squamous and basaloid appearance. No difference between the two groups was found in patient age, presence of adjacent dysplasia, ductal differentiation, or prognosis. There was no correlation between condylomatous tumour morphology and HPV 16 DNA positivity; thus, a subset equivalent to vulval warty carcinoma could not be identified.

Perianal basal cell carcinoma: a comparative histologic, immunohistochemical, and flow cytometric study with basaloid carcinoma of the anus

Perianal basal cell carcinoma is a very rare tumor accounting for only 0.2% of the anorectal tumors. It must be distinguished from basaloid carcinoma of the anus, which resembles it histologically but shows a much more aggressive behavior, metastasizes early, and often proves fatal, thus requiring different therapy. Differential diagnosis of both entities by light microscopy may be difficult. Five cases of perianal basal cell carcinoma and five cases of basaloid carcinoma were studied by means of immunohistochemistry and flow cytometry. Some immunohistochemical markers, such as epithelial membrane antigen, carcinoembrionic antigen, and keratins, as well as the lectin Ulex europaeus agglutinin I stained basaloid carcinoma and were negative for basal cell carcinoma. In contrast, the monoclonal antibody Ber-EP4 seems to be a good marker for perianal basal cell carcinoma and useful in differentiating it from basaloid carcinoma of the anus. Basaloid carcinomas are associated with a significantly higher S-phase fraction than are perianal basal cell carcinomas (p < 0.01).