Re-evaluating silver-stained nucleolar organizer regions (AgNORs) in problematic cutaneous melanocytic lesions: a...

Previous studies enumerating AgNORs in cutaneous melanocytic lesions have produced inconsistent results. It is probable that such inconsistencies arise from differences in fixation, staining technique, and counting strategies. Our group, having demonstrated an improved method of silver staining and having optimized counting, is now able to reconsider the role of AgNORs in evaluating borderline melanocytic lesions. Diagnostic problems similar to those encountered in routine practice have been examined. It is shown that only by counting intra- and extranucleolar AgNORs in combination with assessing the pattern of AgNOR dispersal is it possible to (1) discriminate dysplastic naevi from melanoma and (2) distinguish Spitz naevi and pigmented spindle cell naevi from melanoma. An analysis of AgNOR numbers alone results in considerable overlap between the groups studied. The value of assessing patterns of AgNOR dispersal within and outside clustered nucleolar structures is emphasized. Lesions labelled as minimal deviation melanoma (by experts in dermatopathology) were also investigated. The majority of these specimens form a distinct group lying apart from control naevi and melanomas. This finding, whilst of interest, is difficult to evaluate because of poorly defined diagnostic criteria.