Principles of Melanoma Staging.

Although now commonplace in contemporary cancer care, the systematic approach to classification of disease-specific cancers into a formalized staging system is a relatively modern concept. Overall, the goals of cancer staging are to characterize the status of cancer at a specific moment in time, risk stratify, facilitate prognostication, and inform clinical decision making. The revisions to the American Joint Committee on Cancer (AJCC) melanoma staging system over time reflect changes in our understanding of the biology of the disease. Since the 1st edition, where tumor thickness was defined anatomically by its relationship to the reticular or papillary dermis (Clark level) as well as tumor thickness (Breslow thickness), there have been significant strides in our use of clinicopathological variables to stratify low- versus high-risk patients. Management of the regional nodal basin has also changed dramatically over time, impacted by techniques such as lymphatic mapping and sentinel lymph node biopsy (SLNB) and changes in pathological evaluation of the regional lymph nodes. Additionally, stratification of distant metastases has evolved as survival outcomes have been shown to vary based upon anatomic site of metastases and serum lactate dehydrogenase levels. The variables in use in the current (7th edition) AJCC staging system are surrogate markers of biology with validated impact of survival outcomes. Going forward, it is likely that these and additional clinicopathological factors will be integrated with molecular and other correlates of melanoma tumor biology to further refine and personalize melanoma staging.