Mitotic rate for thin melanomas: should a single mitotic figure warrant a sentinel lymph node biopsy?

BACKGROUND: The seventh edition of the American Joint Committee on Cancer guidelines recognize mitotic rate (MR) as a component of the staging criteria for cutaneous melanomas with a Breslow depth ≤1 mm.

OBJECTIVE: This review discusses the evidence behind the threshold of 1 mitosis per square millimeter as a prognostic variable in thin melanomas, particularly because it relates to the decision to pursue a sentinel lymph node biopsy (SLNB).

MATERIALS AND METHODS: We performed a systematic review using the PubMed database to identify articles that contain prognostic information for thin melanomas based on MR and sentinel lymph node (SLN) status.

RESULTS: Although the threshold of a single mitosis correlates with a statistically significant decrease in survival rates for patients with thin melanomas, the clinical relevance remains questionable particularly because it relates to the decision to pursue an SLNB.

CONCLUSION: A single mitosis in thin melanomas does not increase the risk of a positive SLN so much that SLN biopsy should be routinely performed for this cohort.