Update on the melanoma staging system: the importance of sentinel node staging and primary tumor mitotic rate

Abstract

The 7(th) Edition of the AJCC Staging Manual includes a detailed summary of melanoma staging and prognosis. The revisions are summarized in this article, along with details on two key aspects of melanoma staging: the incorporation of mitotic rate of the primary melanoma and the key role of the sentinel lymph node biopsy (SLNB) in determining accurate staging for clinically occult nodal metastases. Primary tumor mitotic rate was introduced as a major criterion for melanoma staging and prognosis that replaces the Clark's level of invasion, and is now proven to be an important independent adverse predictor of survival. Analysis of the AJCC melanoma staging database demonstrated a significant inverse correlation between primary tumor mitotic rate (histologically defined as mitoses/mm(2) ) and survival. The use of SLNB reliably identifies melanoma patients with nodal micrometastases, enabling clinicians to identify patients with occult nodal metastases that would otherwise take months or years to become clinically palpable The number of nodal metastases was the most significant independent predictor of survival among all patients with stage III disease, including among patients with nodal micrometastases, and continues to be a primary criterion for defining Stage III melanoma. A clinical scoring system model and multivariate predictive tool under the auspices of the AJCC has led to a first-generation web-based predictive tool (www.melanomaprognosis.org).