Longitudinal melanonychia can be caused by melanocyte activation (hypermelanosis) or proliferation (lentigo, nevus or melanoma). Histopathologic examination is mandatory for suspicious cases of melanomas. Tangential biopsy of the matrix is an elegant technique avoiding nail plate dystrophy, but it was unknown whether the depth of the sample obtained by this method is adequate for histopathologic diagnosis. Twenty-two patients with longitudinal melanonychia striata were submitted to tangential matrix biopsies described by Haneke. The tissue was stained with hematoxylin-eosin and the specimens were measured at 3 distinct points according to the total thickness: largest (A), intermediate (B) and narrowest (C) then divided into 4 groups according to the histopathologic diagnosis (G1: hypermelanosis; G2: lentigos; G3: nevus; G4: melanoma). The lesions were measured using the same method. The mean specimen/lesion thickness measure values for each group was: G1: 0,59/0,10？mm, G2: 0,67/0,08？mm, G3: 0,52/0,05？mm, G4: 0,58/0,10？mm. The general average thickness for all the specimens/lesions was 0,59/0,08？mm. We concluded that the tangential excision, for longitudinal melanonychia, provides an adequate material for histopathological diagnosis. 1. Introduction The longitudinal melanonychia can be caused by activation (hypermelanosis) or melanocytic proliferation (lentigo, nevus, or melanoma). The diagnostic accuracy of melanomas presenting as longitudinal melanonychia is low among dermatologists [1]. Thus, biopsy of suspect cases is mandatory. Of all the differential diagnoses [2], melanoma is the more concerning [3, 4]. Among the many techniques in the literature [5–8], the tangential biopsy of the matrix [9] is an elegant alternative providing adequate samples for histopathologic analysis [10], as well as excellent cosmetic results. However, there is still question if the depth of the sample obtained by this method is adequate for histopathologic diagnosis. The goal of this pilot study is to demonstrate that the tangential biopsy of the matrix provides adequate specimens for the pathologist diagnosis in patients with melanonychia striata. 1.1. Material and Methods Twenty-two cases of longitudinal melanonychia underwent matrix tangential biopsy between February 2008 and November 2010. Patients with melanonychia striata were included. Exclusion criteria were presence of Hutchinson’s sing and onychodystrophy. All the biopsies were performed by the same senior dermatologic surgeon based on the technique described by Haneke and Baran [9] (Figures 1 and 2). After
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