A case of subungual melanoma in situ presenting longitudinal melanonychia

A 43-year-old woman presented with two brown longitudinal streaks, which had been present in her left thumb for 5 years. A 3 mm punch biopsy from the nail matrix showed that atypical melanocytes were scattered solitarily in suprabasal and basal layers. Five years after the first visit, she presented with changes of the longitudinal streaks. Two bands were altered into one 0.6cm-sized black pigmented band. There was dystrophy in the distal part of the thumb nail and extension of pigmentation to the skin adjacent to the nail plate, involving the nail fold. Axillary lymph-nodes were not palpable. A longitudinal incisional biopsy revealed increased large atypical melanocytes in suprabasal and basal layers of the epidermis. These findings strongly supported the diagnosis of sublingual melanoma. Our case is interesting in that sublingual melanoma presented longitudinal melanonychia.