Extensive cytogenetic heterogeneity in a benign retroperitoneal schwannoma

A benign retroperitoneal schwannoma from a patient without Drier exposure t o radiotherapy or chemotherapy was analyzed by chromosome banding after sho rt-term culture. An extensive intratumor heterogeneity in the form of 29 ka ryotypically related as well as unrelated clones was found. The aberrant cl ones were diploid or near-diploid and displayed both numerical and structur al changes. All chromosomes, except 11, 16, and 20, were affected. Numerica l changes included trisomies X. 7, 9, 17, and 18, and monosomies 13 and 18. No clonal loss of chromosome 22, the most characteristic abnormality in sc hwannomas of other locations, was, however, detected. The structural aberra tions resulted in a total of 58 chromosomal breakpoints, with chromosomes 1 8, 1, and 15 participating in rearrangements most frequently, followed by c hromosomes 14, 2, and 22. A striking finding was the clonal involvement of 18p11 in eight rearrangements affecting different chromosomes, suggesting a lteration of telomeric function. The molecular mechanisms underlying the ob served massive polyclonality in the schwannoma, particularly the presence o f cytogenetically unrelated clones. are unknown and probably heterogeneous. (C) 2001 Elsevier Science Inc. All rights reserved.