Silver staining of nucleolar organizer regions in malignant melanoma and melanotic nevi

The recently described method of staining nucleolar organizer regions (NOR) with colloidal silver nitrate was applied to the paraffin sections of five junctional nevi, 13 compound nevi, seven Spitz nevi, nine cellular blue nevi, 11 dysplastic nevi, seven malignant lentigines, 12 superficial spreading melanomas, and 14 secondary melanomas. There was a significant difference between the pooled silver-NOR (AgNOR) numbers of the 45 benign lesions (mean, 1.22; SD, 0.51) and the 33 melanomas (mean, 9.18; SD, 4.05) by t test analysis (P less than .01). The difference was striking enough to be recognized on casual microscopic examination, suggesting that AgNOR staining may be a useful technique to help separate melanocytic nevi from malignant melanomas.