skin cancer, a cutaneous neoplasm caused by ionizing radiation; certain genetic defects; chemical carcinogens, including arsenics, petroleum, tar products, and fumes from some molten metals; or overexposure to the sun or other sources of ultraviolet light. Skin cancers, the most common and most curable malignancies, are also the most frequent secondary lesions in patients with cancer in other sites. The major risk factor is overexposure to sunlight. Other risk factors include a fair complexion, xeroderma pigmentosa, vitiligo, senile and seborrheic keratitis, Bowen’s disease, radiation dermatitis, and hereditary basal cell nevus syndrome. The most common skin cancers are basal cell carcinomas and squamous cell carcinomas. Tumors of the sebaceous glands or sweat glands occur infrequently and are adenocarcinomas. Melanoma is a highly metastatic cancer that has increased in incidence during the past 30 years. Basal cell carcinomas, typically raised hard reddish lesions with a pearly surface, rarely metastasize. Scaly, slightly elevated squamous cell tumors may become growths with extensive ulceration and a nonhealing scab. A definitive diagnosis may be established by incisional biopsy or excisional biopsy, which may be the only treatment required for small lesions. Surgery is usually indicated if the lesion is large, if bone or cartilage is invaded, or if lymph nodes are involved. Radiotherapy may be preferable for some smaller facial lesions and is commonly recommended for the treatment of skin tumors without distinct margins. Because of the possibility of recurrence of cancer, surgery is favored for the treatment of younger patients. Despite the curability of skin cancer, it causes many deaths because people fail to obtain treatment. Lesions caused by actinic rays may be prevented by applying a sunscreen. See also melanoma.
