New observations of intraoperative dermoscopic features of the nail matrix and bed in longitudinal melanonychia

Background In recent years, the following four patterns have been defined in intraoperative dermoscopy of the nail matrix and bed in longitudinal melanonychia (LM): (i) a regular gray pattern; (ii) a regular brown pattern; (iii) a regular brown pattern with globules or blotches; and (iv) an irregular pattern. Histopathological findings in these patterns are, respectively: (i) melanocyte activation; (ii) mostly melanocytic hyperplasia (melanocytic activation and melanoma can also be seen); (iii) only melanocytic nevi; and (iv) only melanoma. Objective This study was conducted to compare these patterns with intraoperative dermoscopic findings in another series of five patients with LM. Methods Nail plate dermoscopy, intraoperative nail matrix and bed dermoscopy, and histopathological examinations in five patients with LM were retrospectively reviewed. Results Intraoperative dermoscopy of the nail bed and matrix in patients in whom nail plate dermoscopy demonstrated regular brown lines showed a regular brown pattern with globules in two cases, only globules in one case, and a regular gray pattern in one case. An irregular pattern with globules and blotches was observed in one patient who exhibited irregular brown lines in nail plate dermoscopy. Histopathological examinations showed only hypermelanosis in one case with a regular gray pattern, hypermelanosis and melanophages in cases with a regular brown pattern with globules, blue nevus in one case with an irregular brown pattern with globules and blotches, and only melanophages in one case with globules only. Conclusions Histopathological findings that differ from the patterns previously reported were found. An irregular pattern may also be seen in benign melanocytic nevi such as subungual blue nevus. A globular pattern may be defined as a new pattern corresponding to melanophages only. Additional dermoscopic and histopathological images should be shared to facilitate the development of further understanding and the standardization of the intraoperative dermoscopy of LM.