Nucleolar organizer regions and image analysis nuclear morphometry of small cell (nevoid) melanoma

Small cell (nevoid) melanomas may provide difficulties in diagnosis as their constituent cell type resembles a benign nevoid melanocyte. In the present study, 10 small cell melanomas were analyzed for the silver staining of their nucleolar organizing regions (AgNORs), and their nuclear area and perimeter were measured by computerized digital image analysis and compared with 10 superficial spreading melanomas lacking small cell differentiation and 10 dermal nevi. The average number of AgNORs per nucleus was 5.83 (SD +/- 1.69) for small cell melanomas and was significantly different when compared with 8.49 (SD +/- 1.58) for superficial spreading melanomas (p < 0.05) and 2.71 (SD +/- 0.50) for dermal nevi (p < 0.05). Digital image analysis confirmed that the nuclear perimeter and nuclear area of cells in nevoid melanomas did not significantly differ from those of ordinary dermal nevi (p > 0.05), but both group were significantly different from superficial spreading melanomas lacking a small cell morphology (p < 0.05). Counting AgNOR numbers may be useful in evaluating small cell (nevoid) melanomas and provides a technique for differentiating their constituent cell from ordinary nevus cells. Nuclear morphometry determined by digital image analysis may help better define the nuclear size in small cell melanomas.