Dermoscopic features predicting the presence of mitoses in thin melanoma.

BACKGROUND: The latest AJCC classification has included the number of mitoses as a factor for upstaging thin melanomas. Meanwhile, while dermoscopy has often been used to predict melanoma thickness, its value in predicting number of mitoses remains unknown.

OBJECTIVE: Our aim is to evaluate the correlation between dermoscopic features and the presence of mitoses in a consecutive cohort of thin melanomas.

METHODS: A case control study has been performed to identify specific dermoscopic parameters that could differentiate thin melanomas with 1 or more mitoses per mm2 from those without mitoses.

RESULTS: Of 177 melanomas equal to or thinner than 1mm, 131 (74%) lesions had no mitoses and 46 (36%) lesions had at least 1 mitosis×mm2. Dermoscopic features associated with the presence of 1 or more mitoses were the following: peripheral streaks (OR 4.11; 95% CI 1.94-8.71) and black colour (OR 4.70; 95% CI; 2.28-9.68). In contrast, atypical pigment network (OR (0.30; 95% CI 0.15-0.61)) and brown colour (OR 0.36; 95% CI 0.18-0.75) were associated to melanomas without mitoses. The same variables were also associated to the increasing number of mitoses at linear regression.

CONCLUSION: Black colour and peripheral streaks can predict the presence of mitoses in thin melanoma, while atypical pigment network and brown colour are associated to thin melanoma without mitoses.