Primary cutaneous malignant melanoma.

The prognosis of localized malignant melanoma is related to several histologic features of the primary lesion. Growth pattern, level of invasion, and tumor thickness are currently most widely used in clinical practice, but other features, including ulceration, mitotic rate, density of the inflammatory response, evidence of partial regression, angioinvasion, cell type, cross-sectional profile, and amelanosis have been accorded prognostic significance in single factor analyses. Although stringently controlled prospective studies have yet to demonstrate the validity of these factors for the determination of optimal surgical treatment in individual cases, newer statistical methods of multivariate analysis have made possible assessment of the relative importance of each of these histologic characteristics. The most important and reproducible factor for predicting survival is maximum tumor thickness. Consensus also supports ulceration as another important, independent prognostic indicator, whereas growth pattern and level of invasion derive most of their prognostic value from a secondary correlation with tumor thickness. Mitotic rate may influence survival in the subgroup of patients with high-risk, thick melanomas.