Clinical, dermoscopy and histological correlation study of melanotic pigmentations in excision scars of melanocytic tumours

BACKGROUND: Melanotic pigmentations in scars consecutive to the excision of melanocytic tumours can be secondary to a reactive phenomenon related to the scar tissue or to a recurrence of the melanocytic lesion excised in the first case. Recurrent naevi may sometimes adopt unusual features that make them difficult to differentiate from a melanoma. OBJECTIVES: To describe the clinical, dermoscopic and histological features of melanotic pigmentations in scars consecutive to the excision of melanocytic tumours, and to correlate the histological diagnosis with the dermoscopic features. METHODS: This was a prospective cohort study using macrophotography, dermoscopy and histopathological study. Ninety-five melanotic pigmentations (77 patients) in scars secondary to the excision of melanocytic tumours were prospectively collected in the Department of Dermatology at the Instituto Valenciano de Oncología in Valencia, Spain. Histopathological study was performed in 57 scars. RESULTS: Thirteen dermoscopic structures were identified. Four criteria allowed a differentiation between reactive and specific melanocytic pigmentations. Presence of globules and presence of heterogeneous pigmentation were features associated with specific melanocytic pigmentations (P < 0.0001). Presence of a regular network and presence of streaks were more frequently found in reactive pigmentations (P = 0.023 and 0.026, respectively). CONCLUSIONS: Dermoscopic examination of melanotic pigmentations in excision scars of melanocytic tumours provides useful information about the origin of that pigmentation. Based on such information, recurrent naevi can be differentiated from reactive pigmentations in most cases. Excision and histopathological diagnosis continue to be imperative in some cases of recurrent naevi with atypical clinical features.