The Classification of Cutaneous Melanoma

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Forty years ago, a clinical and histological classification scheme and prognostic factors were described for cutaneous melanoma. This scheme included the subtypes superficial spreading, nodular and lentigo maligna, and prognostic factors including tumor thickness, ulceration, and mitotic activity. There have been some tweaks to the classification scheme, but these basic findings form the foundation for melanoma diagnosis and staging today. Currently, no molecular marker or target has proved reliably useful in the staging or treatment of melanoma. Measurement with a simple ruler serves as the basis for the staging of primary cutaneous melanoma, while the recognition of primary tumor mitotic activity and ulceration also remain significant factors. Recently, mutational analysis has revealed a correlation of activating mutations with the morphological descriptors from decades ago. Future classification schemes may have more power in predicting response to therapy by integrating specific genomic and intra-tumoral expression profiles with histologic findings.

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Existing classification schemes for melanoma

The existing classification schemes for melanoma include the histologic scheme adopted by the WHO9 and the AJCC staging scheme,8 both based on clinical and histologic parameters and both used routinely in the diagnosis and treatment of patients diagnosed with cutaneous melanoma.10 There have also been a handful of proposed genomic classifications, some of which have promise.10 One of these genomic surveys yielded results that validated the original classification of melanoma into subtypes and

Proposals for molecular schemes

After several decades of laboratory-based research, we now have a better understanding of some of the key pathways and potential therapeutic targets in melanoma tumor progression. Although translation of these findings from the research laboratory to clinical practice is in progress, none of these findings has led to a significant change in patient outcome or the development of a robustly effective therapy for any subset of patients with metastatic melanoma. In the future, molecular techniques

Morphologic and genomic classifications come together

An analysis of BRAF and NRAS mutations in coordination with histologic features revealed an aligning of certain histologic findings with BRAF mutation but not with NRAS. The primary tumors that displayed BRAF mutation had a higher frequency of intraepidermal single cell scatter, intraepidermal nesting, increased epidermal thickness, cytologic features that included epithelioid cells and cytoplasmic pigmentation, and a sharp circumscription of the tumor. These features are common to SSMs. This

Summary

Forty years ago a classification scheme and prognostic factors for cutaneous melanoma were described, based on detailed clinical features and histologic analysis, by an international group of authors. In addition to the subtypes—superficial spreading, nodular, lentigo maligna—prognostic factors including tumor thickness, ulceration, and mitotic activity were identified. There have been some tweaks to the classification scheme, but these basic findings form the foundation for the currently

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