One of the goals of the fourth series of Tumor Fascicles is the presentation of new molecular findings which add to our understanding of tumour pathogenesis and may additionally be useful diagnostically. Such information is particularly relevant to the studty of bone tumours and tumour-like lesions and the authors have included an up-to-date summary of where pathologists stand in the application of these new data in this volume. The authors are also well aware that the primary mission of the Fascicles is to aid the practicing pathologist in arriving at the correct diagnosis in a difficult case and for most pathologists any lesion is potentially problematic. Thus the important diagnostic feature of each major lesion (including all variants) is presented in detail. This includes not only the gross, histopathologic and cytologic findings but also the clinical and radiographic features of particular importance in the differential diagnosis of bone tumours and their mimics. NOW WITH ONLINE ACCESS.