A comparative study of Spitz nevus and nodular malignant melanoma using image analysis cytometry.

Image analysis cytometry can be used to estimate both nuclear DNA content and area in tissue sections. Since nodular malignant melanoma and Spitz nevus can show a remarkably similar light microscopic appearance, but may differ in behavior, we studied typical examples of these neoplasms to determine whether cytometric differences existed. Analysis of relative DNA content alone could not discriminate between these 2 entities in the 13 cases that we examined. However, Spitz nevi and nodular melanoma clearly differed in terms of maturation, which we defined as the difference between the mean nuclear size or mean nuclear DNA content of the uppermost and deepest melanocytes in each lesion. Maturation as defined by a decrease in mean nuclear DNA content proved highly significant (p less than 0.005). Only Spitz nevi showed a lesser DNA content in the deepest dermal cells as compared with upper dermal cells, suggesting that some Spitz nevi have an admixture of diploid and hyperdiploid cells in their upper portions, but mostly diploid cells in their deep portions. Only nodular melanoma showed higher mean DNA content in deep dermal cells as opposed to superficial dermal cells, suggesting that some nodular melanomas may either have clones of cells in their deep portions that have higher levels of ploidy, or more cells in the deep portion of melanomas may be in active phases of the cell cycle. Our study suggests that important cytometric differences exist between Spitz nevi and nodular melanoma, and that these could be exploited to develop cytometry into an adjunctive clinical technique.