Is biopsy of the nail matrix necessary to rule out atypia associated with longitudinal melanonychia?  

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 ...