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The evaluation of chondroid lesions requires full integration of clinical, radiographic, and pathological data; tumour typing is often a challenge for the diagnostic pathologist. Although a variety of chromosomal abnormalities have been documented in chondroid lesions, the potential usefulness of cytogenetic analysis remains unclear. This study has critically reviewed and analysed 117 karyotyped samples from 100 patients with cartilaginous and chordoid tumours. Cases were selected based on successful chromosomal analysis and adequacy of clinical, radiographic, and pathological information. To ensure objective evaluation, the cytogenetic results were correlated in a double‐blind setting with consensus diagnoses independently determined on each case, after complete review of the histological, radiographic, and clinical findings. Karyotypic aberrations were identified in 41/92 cartilaginous tumours (5/11 osteochondromas, 2/3 chondromyxoid fibromas, 0/4 chondroblastomas, 11/29 chondromas, 0/3 chondroid tumours of undetermined malignant potential, 22/40 chondrosarcomas and 1/2 miscellaneous cartilaginous lesions) and 5/8 chordomas. Complex karyotypic changes were a feature of malignant tumours (chondrosarcoma and chordoma) and of chondrosarcoma among cartilaginous tumours, where they correlated with high tumour grade. Among primary well‐differentiated cartilaginous lesions of bone, the finding of an abnormal karyotype was consistently associated with a grade 1 chondrosarcoma diagnosis. Among karyotypically abnormal cartilaginous tumours, loss of distal 8q was associated with osteochondroma, +5 with synovial chondroma/chondromatosis and parosteal or soft tissue chondroma, alterations of chromosome arm 6q with chondromyxoid fibroma, +7 with bone chondrosarcoma, and 17p1 alterations with grade 3 chondrosarcoma. Alterations involving 12q13 characterized synovial chondroma/chondromatosis in the chondroma group and myxoid chondrosarcoma of bone in the chondrosarcoma group. In conclusion, cytogenetic abnormalities in chondroid lesions are common and are not randomly distributed. They are associated with malignancy/tumour grade as well as with specific diagnoses in many cases, and can therefore be of potential value for tumour typing. Copyright © 2001 John Wiley & Sons, Ltd.

Identical near-haploid karyotypes with 28, X, +5, +18, +20, +21, +22 were found in two cases of inflammatory leiomyosarcoma, one of which had been reported previously as malignant fibrous histiocytoma. This abnormality may identify these tumours as a separate entity within this group of sarcomas. © 1998 John Wiley & Sons, Ltd.