Noncancerous (benign) and cancerous (malignant) tumors can affect the nail unit, causing a changes in nail texture and/or color (dystrophy).
Noncancerous tumors include myxoid cysts (benign, fluid-filled swellings), pyogenic granulomas, and glomus tumors.
Cancerous tumors include Bowen disease (an early form of skin cancer), squamous cell carcinoma, and malignant melanoma. When doctors suspect cancer, they do a biopsy and may recommend complete removal of the tumor as soon as possible.
A dark band in the nail may be the initial sign of malignant melanoma of the nail. Pigment cells of the nail-making tissue, known as the nail matrix, may become malignant and develop into a melanoma. A worrisome sign is known as Hutchinson sign. The Hutchinson sign is black, brown, or gray discoloration that extends to the area around the nail, such as the cuticle or nail fold (the fold of hard skin at the sides of the nail plate where the nail and the skin meet). This sign may mean there is melanoma in the nail bed (the soft tissue underneath the nail plate that attaches the nail to the finger). When this sign is present, doctors do a biopsy of the nail bed abnormality. Melanoma may also occur without the Hutchinson sign.