[Cytogenetic changes in low grade central osteosarcomas].

Low grade central osteosarcomas are a group of rare bone neoplasms morphologically simulating benign bone tumors or tumor-like lesions (fibrous dysplasia, nonossifying fibroma, osteoblastoma, chondromyxoidfibroma or aneurysmal bone cyst). Because of the apparent bland histology they may be misinterpreted as benign lesions despite their primary low malignant behavior and late metastatic potential including the capability to transform into a highly malignant sarcoma. In contrast to high grade osteosarcomas cytogenetic studies of these entities are very rare. Karyotyping including FISH analysis with painting- and centromere-specific probes was done in 2 cases of low grade central osteosarcomas (fibrous dysplasia like type). One case was a primary lesion in the upper femur, the other was a recurrent lesion in the upper humerus. Additionally a static DNA cytometry using Feulgen stained imprints was carried out in both cases. In the first case clonal aberrations with a Robertsonian translocation between chromosomes #14 und #15, balanced translocations including chromosomes #5 and #21, #12 and #20, and a supernumary ring chromosome derived from chromosome #1 were detected in a near diploid karyotype. The second case displayed the development from a DNA-diploid to a DNA-peritetraploid lesion during a follow up of six years. Cytogenetic different marker chromosomes and again ring chromosomes were detected in a near tetraploid karyotype. Low grade central osteosarcomas of fibrous dysplasia like type may be characterized by chromosomal aberrations including ring chromosomes. Regarding the last feature these cytogenetic findings resemble those found in low grade parosteal osteosarcomas and other mesenchymal lesions of borderline behavior or low malignancy grade (for example dermatofibrosarcoma protuberans, low grade liposarcoma).