Longitudinal melonychia: clinical evaluation and biopsy technique.

Longitudinal melonychia is a brown streaking of the nailbed. It is often benign but can be a subungual melanoma. Subungual melanoma is a rare malignancy. Diagnosis is often delayed, resulting in a higher staging and poorer prognosis than other cutaneous melanomas. We provide an update on the evaluation of longitudinal melonychia and biopsy technique.