Sentinel node biopsy should be offered in thin melanoma with mitotic rate greater than one.

Background: The American Joint Committee on Cancer recently added mitotic rate (MR) to their seventh edition staging system for melanomas, which went into effect on January 1, 2010. MR has replaced the Clark level of invasion for T1 melanomas. Dermatologists and dermatopathologists should be aware of these new guidelines.

Objective: To clarify how MR may be used to determine the prognosis of thin melanomas and to identify patients with thin melanomas who would be candidates for a sentinel lymph node biopsy (SLNB).

Methods: Reports in the literature were reviewed regarding mitotic rate in thin melanomas and the use of MR for prognosis and as an indication for SLNB.

Results: Multiple studies have shown MR to be a significant prognostic factor, surpassing Clark level of invasion, in patients with thin melanomas. SLNB is the best prognostic method for staging T1b (<1 mm thick with MR ≥1 or ulceration), T2, T3, and T4 melanomas, and SLNB should be discussed and offered to these patients.

Conclusions: Multiple studies support the use of MR in staging for thin melanomas, and patients with a high MR should be considered for SLNB.