Malignant melanoma is the most dangerous type of skin cancer. Melanomas beneath the fingernail appear as a black or bluish black discoloration. This type of malignancy spreads (metastasizes) readily.
Review Date 2/27/2018
Updated by: David L. Swanson, MD, Vice Chair of Medical Dermatology, Associate Professor of Dermatology, Mayo Medical School, Scottsdale, AZ. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.