In about two-thirds of people with nail melanoma, the main symptom is longitudinal melanonychia, a dark vertical streak or line under the nail plate. It may be thin or thick, and light brown to black.

Subungual melanoma, or nail melanoma, is skin cancer under your nail. It usually appears as a dark, vertical streak on your nail. Subungual melanoma is rare but serious. Unlike other skin cancers ...

Melanonychia typically appears as a vertical (longitudinal) streak running from the cuticle ... of developing black lines on ...