Background: Recently, the quantification of mitoses in cutaneous melanoma has been discharged from the main prognostic variables of the TNM classification.
Objective: To investigate the prognostic value of the presence of mitoses in primary cutaneous melanoma and to establish the number of mitoses per mm2 that may have prognostic significance.
Methods: A retrospective observational study was performed on 141 patients treated for cutaneous melanoma, who were assessed by the same pathologist, and who had a minimum follow-up of 2 years. Clinical, epidemiological, histopathological and follow-up variables were gathered and compared with the number of mitoses to distinguish the significance of differences by means of univariate, multivariate, and survival analyses.
Results: The cut-off level related to a better sensitivity and specificity was 1.50 mitoses per mm2. The presence of two or more mitoses/mm2 showed a better relationship with prognostic variables and both the overall and disease-free survival than the presence of 1 or more mitoses/mm2. This happens especially in melanomas thicker than 0.8 mm and it could affect the staging in cases with Breslow between 1 and 2 mm.
Conclusions: A mitotic rate of two or more mitoses per mm2 in cutaneous melanoma should be considered as a more accurate prognostic factor than one or more mitoses per mm2, particularly in tumors equal or greater than 0.8 mm in thickness.
Keywords: Cut-off; Cutaneous melanoma; Mitosis; Prognostic.