[Recurrent basal cell epitheliomas and those developing on pre-existing lesions (author's transl)].

Cancerous changes occur most frequently in four types of chronic acquired lesions: rare lupus scars and those of long-standing burns, rhinophymas, and radiodermatitis. Insufficient therapy is often applied because of underestimation of potential changes, fear of hemorrhage, or lack of knowledge of the extent of the lesion. The ulcerous forms and those developing in scar tissue have the poorest prognosis, and this also applies to centrofacial basal cell epitheliomas. Recurrences after radiotherapy are of bad omen, and they must be treated by wide surgical excision.