CYTOGENETIC INTRATUMOR HETEROGENEITY IN SOFT-TISSUE TUMORS

Multiple (two to seven) samples, obtained from the same surgical speci men or at different occasions, were analyzed in 54 benign and malignan t soft tissue tumors, to investigate cytogenetic clonal evolution. In 28 tumors only normal karyotypes were found. Ten tumors had abnormal k aryotypes, but were noninformative, most often due to a high level of karyotypic complexity or great cell-to-cell variation. Sixteen tumors were informative: four (leiomyosarcoma, liposarcoma, malignant Schwann oma, and a benign mesenchymal tumor, probably leiomyoma) had identical karyotypes in different samples, whereas the remaining 12 tumors (sev en malignant fibrous histiocytomas [MFH], two leiomyosarcomas, two lip osarcomas, and one synovial sarcoma) displayed intersample heterogenei ty. Also, intrasample heterogeneity was detected; more than one clone was found in 21 of 73 samples with aberrations from 26 tumors. The dif ferent clones were related in all cases except two. In seven cases, sa mples from different occasions were studied, and clonal evolution coul d be evidenced in five of them, whereas in two cases the karyotypes re mained unchanged. The results indicate that the acquisition of ring ch romosomes is an early event in the development of MFH and possibly als o pleomorphic liposarcoma. The findings, together with previous data, also indicate that rearrangements of 19p13 are late events in the prog ression of pleomorphic sarcomas. The overall conclusion from this stud y is that cytogenetic heterogeneity is common in soft tissue tumors, a nd that this might influence the evaluation of cytogenetic and molecul ar genetic findings.