Since longitudinal melanonychia arises in the nail matrix, the nail matrix must be biopsied to rule out a melanoma. While a punch biopsy can be performed, a tangential shave of the matrix gives a more complete sample to the pathologist and causes less dystrophy. In both cases, the proximal nail fold...

Yes. A nail matrix biopsy is the only way to rule out atypia due to longitudinal melanonychia.

I want to add that I have also found it helpful to thin the target area of the nail plate via: sanding with an emery board with a dermablade A quick tourniquet to help with hemostasis can be made by cutting the long finger of a glove, and making an opening at the distal end so that it can be ...