Analysis of melanocytic lesions by DNA image cytometry

There is increasing evidence that melanocytic nevi with architectural and/or cytologic atypia (dysplastic melanocytic nevi [DMN]) are lesions intermediate between banal nevi and malignant melanoma. Other studies have shown conflicting results regarding the DNA content in DMN.

In the present investigation, the authors measured DNA ploidy by image analysis (CAS-200 system, Cell Analysis Systems, Inc., Elmhurst, IL) using Feulgen staining in 54 melanocytic lesions. The lesions were categorized into 7 groups: compound nevus (CN) = 7; compound nevi with features of DMN (F) = 10; DMN with slight atypia = 8; DMN with moderate atypia = 9; DMN with severe atypia (S) = 8; melanoma in situ = 5; and malignant melanoma (CMM) = 7. The age distribution for these various lesions was also recorded. DNA histograms obtained by image analysis from these groups were examined for DNA aneuploidy by DNA index and classified according to Auer classifications (Auer I-IV).

There was a progression of mean age for each group of melanocytic lesions, ranging from 39 years for ordinary nevi to 53 years for invasive melanoma. The Type I histogram, which is distinctly diploid, was seen in 4 of 7 cases of CN, 5 of 10 of nevi with features of dysplastic nevus, and 3 of 8 nevi with slight atypia. The Type I histogram was not observed at all in nevi with moderate atypia, severe atypia, melanoma in situ, and invasive melanoma. The Type IV histogram (aneuploid) was not identified in low grade lesions (CN, F, S), but was observed in two of nine nevi with moderate atypia, six of eight lesions with severe atypia, two of five melanomas in situ, and five of six invasive melanomas. Aneuploidy by DNA index was noted in one nevus with features of DMN, one DMN with slight atypia, one with moderate atypia, four of eight DMN with severe atypia, two of five in situ melanomas, and two of six invasive melanomas.

The results show that DMN exhibit a spectrum of abnormal DNA content intermediate between banal nevi and CMM and that DNA content generally correlates with the age of patients and degree of atypia in melanocytic nevi.