Nucleolar organizer regions in malignant melanoma and melanocytic nevi. Comparison of two counting methods.

Using a silver staining technique, we studied nucleolar organizer regions (AgNOR) in paraffin sections of junctional nevi, compound nevi, intradermal nevi, blue nevi, dysplastic nevi, Spitz nevi, lentigo maligna, malignant melanomas in nevus, superficial spreading melanomas, and nodular melanomas. Two methods of counting black dots within nuclei were employed. One method was to count the discrete black dots within the nuclei, including the tiny black dots seen within the nucleolus; the second method did not take into account the subsidiary cluster of tiny black dots seen within the nucleolus, instead treating these dots as a single structure. Whichever method we used, a significant difference was found between the pooled mean AgNOR numbers for benign and malignant lesions. We found an overlap, however, between benign, in particular Spitz and dysplastic nevi, and malignant lesions when considering individual counts of AgNOR using both methods. We conclude that studying AgNOR does not seem to be a useful technique to differentiate Spitz and dysplastic nevi from malignant melanomas.