[Precancerous skin lesions in the aged (author's transl)].

The term "precancerous" needs a new definition since it includes still malignant diseases like Morbus Paget of the nipple, Morbus Bowen and Erythroplasie Queyrat. The degree of malignancy of these disorders is analyzed. Precancerous conditions in the sense of benignant disorders which necessarily develop into malignant tumors are Melanosis circumscripta praeblastomatosa Dubreuilh and actinic keratoses. Potential precanceroses may be X-ray-atrophy, Leukoplakia and oral papillomatosis. Some actinic, chemic and cytostatic cancerogens are mentioned. Reference is made to the diagnosis, differential diagnosis, prognosis and treatment of precancerous skin lesions. The problem of potential malignancy of nevi is considered in detail. Prevention of cancer needs regular careful clinical control of skin and mucous membranes at least after the 50th year of life.