[The problem of malignant degeneration in case of multiple neurofibromatosis (author's transl)].

Within less than one year, our hospital received three cases of malignant manifestation in case of multiple neurofibromatosis. If the histological findings and the neurogenic origin of the malignant tumor are evaluated very critically, the malignant suppression of the differentiation of one or more neurofibromas in case of multiple neurofibromatosis must be considered as occuring very rarely. If in case of a neurofibromatosis a malignant manifestation is found, it has to be examined very carefully by tissue specimens of numerous spots (Loehr and Willebrand), furthermore the neurogenic origin must be ensured (Zuelch). There are three clinical possibilities: 1. Sarcomatous degeneration of a neurofibroma with demonstrable neurogenic origin. 2. Histological appearence of a malignant suppression of the differntiation of a neurofibroma with benign clinical course. 3. Independent sarcoma as second disease without original connection to an existing multiple neurofibromatosis.--A critical evaluation of our cases showed that there was only one case of malignant tumor with neurogenic origin, namely a neurofibrosarcoma originating from a multiple neurofibromatosis.