Skin Cancers (Keratoses)
Scaly patches on the skin, on the face, such as ear and nose and back of the hands. Patches also appear on the scalp. These develop in the very elderly, usually on areas exposed to sun. It is caused by too much exposure of fair skin to sun or due to X-ray treatment or exposure to toxic chemicals.

The frequency of skin cancer is proportional to the duration of immunosuppression and the extent of sun exposure. Skin cancer is a not uncommon finding in patients infected with HIV, and it may be more aggressive in this setting.

Nonmelanoma skin cancer is the most common cancer in the United States, with an estimated annual incidence of more than 1,000,000 cases. Basal cell carcinomas (BCCs) account for 70 to 80% of nonmelanoma skin cancers. Squamous cell carcinomas (SCCs), while representing only about 20% of nonmelanoma skin cancers, are more significant because of their ability to metastasize; they account for most of the 2300 deaths annually. Incidence rates have risen dramatically over the past decade.

Cause of skin cancer

Cumulative exposure to sunlight, principally the ultraviolet B (UV-B) spectrum, is the most significant factor. Other factors associated with a higher incidence of skin cancer are male sex, older age, Celtic descent, a fair complexion, a tendency to sunburn easily, and an outdoor occupation. The incidence of these tumors increases with decreasing latitude.

As the earth's protective ozone shield continues to thin, further increases in the incidence of skin cancer can be anticipated. In certain geographic areas, exposure to arsenic in well water or from industrial sources may significantly increase the risk of BCC and SCC. Skin cancer in affected individuals may be seen with or without other cutaneous markers of chronic arsenism (e.g., arsenical keratoses). Less common is exposure to the cyclic aromatic hydrocarbons in tar, soot, or shale.

Treatment of skin cancer

The treatment should be done at a very early stage by radio-therapy, surgery and cryotherapy (liquid nitrogen can be used to kill cancer cells by freezing). Lasers also have been used for the treatment of skin cancer.