[Cartilage tumors: morphology, genetics, and current aspects of target therapy].

Cartilage tumors are a heterogeneous group of mesenchymal tumors whose common characteristic is the formation of a chondroblastic differentiated groundsubstance by the tumor cells. The basic features of their histological classification were already developed in the 1940s and supplemented by further entities in the following decades. Only in the past 10-15 years have fundamental new insights been gained through molecular genetic analysis. So, osteochondromas are characterized by alterations in the EXT1 and EXT2 genes. The description of mutations of isocitrate dehydrogenase 1 and 2 (IDH 1 and 2) in chondromas and chondrosarcomas is particularly important. The mesenchymal chondrosarcoma is characterized by a fusion of the HEY1-NCOA2 genes. The molecular genetic alterations characteristic for the individual tumor entities are first of all an essential supplement for the differential diagnosis of radiologically and histologically difficult cases. They also provide the basis for the establishment of molecular target therapies for malignant chondrogenic tumors. This applies in particular to conventional chondrosarcoma, for which all approaches to chemo- and radiotherapy have proven to be ineffective. However, the use of target therapies is still in its beginnings.