Summery. Bone tumors vary widely in their biological behavior. Standard pathologic procedures and morphologic examination of the specimens is an attempt to better understand the nature of the tumor, predict the behavior of malignant sarcomas and validate the diagnosis. In our routine work we succeeded because of everyday friendly support from collaboration of pathologists. We especially want to thank for all their time, knowledge and expert opinion our colleague from Mayo Clinic Rochester Minnesota (professors: Carrie Y. Inwards, Andrew L. Folpe, Andre M. Oliveira) and Istituto Ortopedico Rizzoli (Franco Bertoni and Patrizia Bacchini).