Benign and malignant tumors can affect the nail unit, causing a deformity. These tumors include noncancerous myxoid cysts, pyogenic granulomas, glomus tumors, Bowen's disease (an early form of skin cancer), squamous cell carcinoma, and malignant melanoma. When doctors suspect cancer, they perform a biopsy and may recommend complete removal of the tumor as soon as possible.

Hutchinson's sign—a black discoloration of the area around the nail, including the lunula (half-moon at the base of the nail), cuticle, and nail fold (the fold of hard skin overlapping the sides of the nail)—may mean there is cancer in the nail bed. When this sign is present, doctors perform a biopsy and begin treatment as quickly as possible.

Last full review/revision August 2007 by Wingfield E. Rehmus, MD, MPH