Nuclear parameters in the superficial and deep portion of melanocytic lesions--a morphometrical investigation.

Morphometric techniques in diagnostic pathology of pigmented skin lesions are not yet well established. The so-called maturation of melanocytes (nevus cells) with progressive descent into the dermis is one important criterion to differentiate benign from malignant melanocytic lesions in conventional histology. We therefore examined morphometrically the nuclear parameters of melanocytes (nevus cells) in the superficial and deep portion of 120 pigmented skin tumors (40 cases each of malignant melanoma. Spitz's nevus and benign dermal nevus) with special emphasis on the "maturation to the depth". A "maturation parameter" (MP) was assessed in each individual case, calculating the ratio of the nuclear area in the deep portion and in the superficial portion. The mean values of MP were 0.720 +/- 0.11 for dermal nevi, 0.725 +/- 0.10 for Spitz's nevi and 1.125 +/- 0.11 for malignant melanoma. The difference between malignant melanoma and both groups of benign nevi was statistically significant (p less than or equal to 0.01). The efficiency of the maturation parameter was 0.95 for the distinction of dermal nevi and malignant melanomas, and 0.97 for the distinction of Spitz's nevi and malignant melanoma. Measurements of the superficial portion only revealed comparatively low efficiency values (0.70 and 0.56, respectively). Our results indicate that morphometric evaluations of the nuclear area of melanocytes (nevus cells) in the deep portion of the infiltrate are more discriminative than those in the superficial portions. The establishment of the MP allows a better differentiation between benign and malignant melanocytic lesions and therefore morphometric methods may obviously be a helpful tool in the diagnosis of melanocytic skin tumors.