MORPHOLOGICAL AND IMMUNOHISTOCHEMICAL SPECTRUM IN ANORECTAL MALIGNANCIES

The morphological features of 62 anorectal malignancies diagnosed on s igmoidoscopic biopsy were studied. On haemotoxylin and eosin staining the tumours were diagnosed as adenocarcinomas (43), squamous cell carc inoma (12), malignant melanoma (3), carcinoid (2), clear cell carcinom a (1) and poorly differentiated carcinoma (1). PAS Alcian blue, Grimel ius silver stain, AgNOR and immunohistochemical stain for carcinoembry onic antigen (CEA) and human papilloma virus (HPV) were done to furthe r categorise these tumours. The ages of the patients varied from 18 to 77 yr (mean 43.7 yr) and the male : female ratio was 2:1. PAS Alcian blue staining was helpful in differentiating mucinous from non-mucinou s adenocarcinomas and reclassifying one poorly differentiated carcinom a as mucin secreting adenocarcinoma. Also, it clearly identified paget oid spread in two cases of adenocarcinomas. Grimelius silver stain was strongly positive in melanomas and neuroendocrine tumours. Basal silv er staining was visualised in metaplastic foci but was absent in dyspl astic epithelium. AgNOR counts may be considered useful in differentia ting melanomas (high counts) from spindle cell variant of squamous cel l carcinomas (low counts). High AgNOR counts and strong Grimelius posi tivity in clear cell carcinoma suggested its melanotic origin. Immunos taining for CEA and HPV were of limited value. CEA was positive in the majority of the adenocarcinomas while HPV could only be demonstrated in two squamous cell carcinomas.