Noncancerous (benign) and cancerous (malignant) tumors can affect the nail unit, causing a changes in nail texture and/or color (dystrophy Deformities, Dystrophies, and Discoloration of the Nails The terms deformities and dystrophies are often used interchangeably, sometimes even by doctors. However, their meanings are slightly different. Deformities: Changes in nail shape... read more 
). Many of these are tumors that originate in tissues around but not in the nail.
Noncancerous tumors include myxoid cysts (benign, fluid-filled swellings), pyogenic granulomas Pyogenic Granulomas Pyogenic granulomas are fleshy, moist or crusty, and red or reddish brown slightly raised bumps caused by an increased growth of capillaries (the smallest blood vessels) and swelling of the... read more 
, and glomus tumors.
Cancerous tumors include Bowen disease Bowen Disease Bowen disease is an early form of squamous cell carcinoma that is confined to the outer layer of the skin (epidermis) and has not yet invaded the deeper layers. Bowen disease most commonly occurs... read more 
(an early form of skin cancer), squamous cell carcinoma Squamous Cell Carcinoma Squamous cell carcinoma is cancer that begins in the squamous cells of the skin. Thick, scaly growths appear on the skin and do not heal. To diagnose the cancer, doctors do a biopsy. Treatment... read more 
, and malignant melanoma Melanoma Melanoma is a skin cancer that begins in the pigment-producing cells of the skin (melanocytes). Melanomas can begin on normal skin or in existing moles. They may be irregular, flat or raised... read more 
. 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.
