Histological demarcation of lateral borders: an unsupportable criterion for distinguishing malignant melanoma from Spitz naevus and compound naevus.

AIMS

The objective of this study was to determine the validity of sharpness of lateral margins (an important component of the pattern analysis method) as a criterion for the histological distinction of naevi from malignant melanoma.

METHODS AND RESULTS

The sharpness of lateral borders in a series of histologically unequivocal malignant melanomas, Spitz naevi and compound naevi, chosen at random from dermatopathology slide archives, was determined. The incidence of poor demarcation of lateral borders in malignant melanomas was about equal to that of Spitz naevi and was significantly less than in compound naevi. The sharpness of lateral borders frequently varies with level of sectioning.

CONCLUSIONS

The proposal that malignant melanomas have a significantly greater incidence of poor demarcation of lateral borders than benign melanocytic neoplasms (Spitz naevi and compound naevi) was shown to be without validity on cited empirical grounds as well as theoretical grounds (the lack of constancy of pattern from a 3-dimensional standpoint).