LAUSR

BACKGROUND Nail matrix histopathological examination is essential to diagnose longitudinal melanonychia (LM). Several methods for nail matrix biopsy have been introduced but are often difficult to perform because of their invasiveness and technical difficulty. Therefore, a less invasive and novel biopsy technique is needed. OBJECTIVE To introduce a window technique for nail matrix biopsy. MATERIALS AND METHODS We retrospectively reviewed the medical records and histopathological specimens of patients with LM who underwent the window technique for nail matrix biopsy at our institution between September 2015 and December 2016. RESULTS Eleven cases from 10 patients with LM were subjected to our tailored window technique assisted by carbon dioxide (CO2) laser and dermoscopy. We performed nail plate dermoscopy to select the biopsy site and used CO2 laser to create the window in the proximal nail plate. Nail matrix pigmentation was carefully investigated using intraoperative dermoscopy. The technique established appropriate diagnosis in 11 LM cases, without significant complications, as follows: melanoma in situ (4 cases) and nail matrix activation (7 cases). CONCLUSION The window technique assisted by CO2 laser and dermoscopy can be a minimally invasive and effective method for nail matrix LM biopsy under local anesthesia.