CHROMOSOME-ABERRATIONS AND CYTOGENETIC INTRATUMOR HETEROGENEITY IN CHONDROSARCOMAS

Clonal chromosome aberrations identified after short-term culture are presented for 13 chondrosarcomas; in 5 cases both the primary tumors a nd local recurrences were studied. The stemline chromosome number was hypodiploid or hyperhaploid in 9 tumors. The most frequent numerical a nomalies were, in falling order of frequency, loss of chromosomes Y, 1 0, 13, and 6, and gain of chromosomes 7 and 20. No recurrent structura l rearrangement was found, but chromosome bands 5q13, 1q21, 7p11, and 20q11 were each involved in three different rearrangements. Karyotypic heterogeneity was assessed in two different ways: as the presence of more than one clone in one sample and as the presence of different clo nes in different samples from the same surgical specimen. Clonal karyo typic evolution was demonstrated in 6 of the 7 cases in which two or m ore samples could be investigated. All 6 showed intersample heterogene ity. Intrasample heterogeneity was found in only 5 of the 28 samples w ith aberrations. By comparing the incidences of the nonrandomly occurr ing aberrations in stemlines and sidelines in the heterogeneous tumors , it was possible to conclude that loss of chromosome 13 and rearrange ment of band 5q13 were early events in the clonal evolution.