The importance of mitosis as a factor for predicting sentinel lymph node biopsy for thin melanoma.

23-year-old female patient, with superficial spreading melanoma (SSM) on the back, Breslow 0.35 mm, Clark II, without ulceration and with 2 mitosis/mm². Patient was submitted to margin enlargement and sentinel biopsy of 2 lymph nodes (left armpit). Histopathology revealed micrometastasis in the subcapsular sinus of both. Following the recommendation of the 2009 American Joint Committee on Cancer Melanoma Staging (AJCC), the patient underwent complete axillary lymphadenectomy. No other lymph nodes were metastatic. The clinical application of dermoscopy has enabled more accurate diagnosis of cutaneous melanoma, probably contributing to a greater proportion of thin melanomas at diagnosis. The mitotic rate was included as an important prognostic factor for thin melanomas by the AJCC, suggesting biopsy for these patients.