Pathology and prognostic factors.

Abstract

Cutaneous malignant melanoma and its precursors were the general subjects of the National Institutes of Health Consensus Conference held in January 1992. Particular emphasis was placed on the diagnosis of early melanoma, especially melanoma in situ, and the controversies surrounding dysplastic nevi. Recent studies of unusual nevi often confused with melanoma, eg, deep-penetrating (plexiform) nevus, combined nevus, desmoplastic melanocytic nevus, and Spitz nevus in childhood, provided detailed histologic criteria for their discrimination from melanoma. Rare or unusual forms of melanoma, including desmoplastic melanoma, neurotropic melanoma, a newly described variant angiotrophic melanoma, subungual melanoma, and balloon cell melanoma have been the subject of comprehensive histologic studies. Other histopathologic investigations have described the prevalence of histologic regression and intraepidermal pagetoid spread in melanomas and the histologic features of reexcision specimens of melanoma. New evidence suggests that the predominant cell type infiltrating melanoma is the monocyte-macrophage, and the expression of monocyte chemotactic protein-1 by melanoma may explain the recruitment of this cell type. Immunopathologic studies of melanocytic lesions were performed with various melanocyte-associated antigens (eg, HMB-45), proliferation antigens (eg, Ki-67), and progression markers (eg, epidermal growth factor receptor and HLA-DR). HMB-45 binding has been localized ultrastructurally to early melanosome formation. Various prognostic factors, including gender, high-risk anatomic sites (particularly the scalp), race (black vs white patients), microscopic satellites, tumor volume, indices of proliferation and tumor cell motility, volume-weighted mean nuclear volume, DNA ploidy, and nucleolar organizer regions have been the subject of recent investigations. Analysis of many patients with long-term follow-up has facilitated better prognostic modeling of melanoma.