We read with interest the article by Cassarino et al1 titled “Primary Dermal Melanoma: Distinct Immunohistochemical Findings and Clinical Outcome Compared With Nodular and Metastatic Melanoma” in the January 2008 issue of the Archives. The authors provide a compelling argument that primary dermal melanomas (PDMs) have improved survival compared with metastatic melanoma or primary nodular melanoma of the same Breslow thickness. In the past, cases of PDM would have been classified as either nodular or metastatic melanoma, and patients would have been given prognostic information that may not have been correct.2 Purely desmoplastic melanomas have also been shown to have a prognosis different from that of superficial spreading melanomas of the same thickness.3 Dermatopathologists have come to recognize differences in the biologic behavior of certain types of melanoma and have come to understand that light microscopic findings may not always allow distinction of nevi from melanoma.4,5 The cases reported by Cassarino et al1 as well as recent studies highlighting the limitations of routine microscopic diagnosis of melanoma provide compelling evidence that melanoma is more complex than previously suspected.4-7 All melanomas of the same Breslow thickness do not have the same biologic potential for metastasis, and routine microscopic studies may not always allow for an indubitable diagnosis of melanoma. It is likely that detailed genetic information will overshadow the importance of the histologic attributes of certain types of melanocytic proliferations.8 Clinicians need to be aware that many serious researchers are questioning long-held assumptions about melanoma and are finding surprising results.
Helm TN, Helm KF. More Evidence for a New Melanoma Paradigm. Arch Dermatol. 2008;144(7):946–947. doi:10.1001/archderm.144.7.946-b
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