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Update on Thin Melanoma: Outcome of an International Workshop
Daniela Mihic-Probst1, Chris Shea, Lyn Duncan
1*Department of Surgical Pathology, University Hospital Zürich, Zürich, Switzerland †Department of Dermatology, University of Chicago, IL ‡Dermatopathology Unit, Massachusetts General Hospital, Harvard Medical School, Boston, MA **Departments of Dermatology and Pathology, University of Michigan, Ann Arbor, MI §§Myriad Genetic Laboratories Inc., Salt Lake City, UT ∥∥Departments of Pathology and Cell Biology and Dermatology, University of South Florida Morsani College of Medicine, Tampa, FL ¶¶Department of Pathology and Laboratory Medicine, Hospital of the University of Pennsylvania, PA §Departement de Biopathologie, Centre Léon Bérard, Lyon ##Department of Pathology, Institut Curie, Paris, France ∥Escola Paulista de Medicina, Universidade de São Paulo, Brasil ¶Department of Molecular Immunology and Cell Biology, Life and Medical Sciences Institute, University of Bonn, Germany #Laboratory of Translational Cell and Tissue Research and University Hospitals, University of Leuven, KUL, Leuven, Belgium ††Department of Molecular Oncology, CRUK Manchester Institute Royal Surrey County Hospital, Guildford, UK ‡‡Department of Dermatology, Chonnam National University Medical School, Gwangju, Korea.
Abstract:
The following communication summarizes the proceedings of a 1-day Workshop of the International Melanoma Pathology Study Group, which was devoted to thin melanoma. The definitions and histologic criteria for thin melanoma were reviewed. The principal differential diagnostic problems mentioned included the distinction of thin melanoma from nevi, especially from nevi of special site, irritated nevi, inflamed and regressing nevi, and dysplastic nevi. Histologic criteria for this analysis were discussed and the importance of clinico-pathologic correlation, especially in acral sites, was emphasized. Criteria for the minimal definition of invasion were also discussed. In addition, a new technique of m-RNA expression profiling with 14 genes was presented and facilitated the distinction of thin melanomas from nevus in histologically obvious cases. However, for particular nevi, it was not obvious why the results indicated a malignant lesion. Despite many molecular and other ancillary investigations, Breslow thickness remains the most important prognostic factor in thin melanoma. The prognostic significance of radial (horizontal) and vertical growth phases, Clark level, regression, and mitotic rate were also discussed. Because of the increasing frequency of thin melanomas, there is a great need to develop more refined predictors of thin melanomas with worse clinical outcome.
