Cancer is any malignant growth or tumor caused by abnormal and uncontrolled cell division.  Cancer may spread to other parts of the body through the lymphatic system or the blood stream. The carcinogenic effects of doses of 100 rads (1 Gy) or more of gamma radiation delivered at high dose rates are well documented, consistent and definitive.

Skin cancer can appear after high doses of radiation.Although any organ or tissue may develop a tumor after overexposure to radiation, certain organs and tissues seem to be more sensitive in this respect than others. Radiation-induced cancer is observed most frequently in the hemopoietic system, in the thyroid, in the bone, and in the skin.  In all these cases, the tumor induction time in man is relatively long - on the order of 5 to 20 years after exposure.

Carcinoma of the skin was the first type of malignancy that was associated with exposure to x-rays. Early x-ray workers, including physicists and physicians, had a much higher incidence of skin cancer than could be expected from random occurrences of this disease. Well over 100 cases of radiation induced skin cancer are documented in the literature. As early as 1900, a physician who had been using x-rays in his practice described the irritating effects of x-rays. He recorded that erythema and itching progressed to hyper-pigmentation, ulceration, neoplasia, and finally death from metastatic carcinoma. The entire disease process spanned a period of 9 years. Cancer of the fingers was an occupational disease common among dentists before the carcinogenic properties of x-rays were well understood. Dentists would hold the dental x-ray film in the mouths of patients while x-raying their teeth.