[Instrumental diagnosis for therapy decision making--what is possible and desirable, what is essential and what is superfluous?].

With knowledge of the classical radiological characteristics of benign and malignant bone tumors, taking age and localization of lesion into consideration, and with the help of classification according to Lodwick, 90% of all cases can be diagnosed. Compared with benign lesions, malignant tumors are quite rare, so those with less experience are advised--in case of doubt--to carry out a reference evaluation, since further imaging, e.g., costly magnetic resonance imaging (MRI), is in general not of any help for diagnosis. Only when malignancy is suspected or to plan biopsy is MRI, however, not only desirable to outline the malignant lesion in bone and soft tissue, but is an absolutely necessary in modern interdisciplinary treatment concepts, without which extremity-conserving surgery with constantly increasing life expectancy together with the considerable success of chemotherapy would be unthinkable.