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Malignant peripheral nerve sheath tumors (MPNST) are rare soft-tissue malignancies. The genetic basis of these tumors is still poorly understood. Cytogenetic analyses predominantly revealed complex karyotypes, precluding the identification of recurrent chromosomal changes. We report loss of 1p material in a near-diploid karyotype with few or no additional structural chromosome changes in two sporadic cases of MPNST, indicating an important role of 1p loss in MPNST development. In one of these two tumors, a distal 1p deletion (1p31.2 approximately pter) was detected suggesting involvement of a tumor suppressor gene located within this distal region of 1p. Further evidence for recurrent 1p loss in MPNST was obtained by interphase fluorescence in situ hybridization, which showed loss of 1p material in 3 out of 13 tumors. These findings together with data from the literature suggest that loss of a tumor suppressor gene located within distal 1p is implicated in the pathogenesis of MPNST.

Comparative genomic hybridization (CGH) analysis was performed on 36 neuroblastomas of both low and high stage of disease. This study significantly increases the number of neuroblastoma tumors studied by CGH. Analysis of larger series of tumors is particularly important in view of the different clinical subgroups that are recognized for this tumor. The present data and a comparison with all published CGH data on neuroblastoma provide further insights into the genetic heterogeneity of neuroblastoma. Stage 1, 2, and 4S tumors showed predominantly whole chromosome gains and losses. A similar pattern of whole chromosome imbalances, although less frequent, was observed in stage 3 and 4 tumors, in addition to partial chromosome gains and losses. An increase in chromosome 17 or 17q copy number was observed in 81% of tumors. The most frequent losses, either through partial or whole chromosome underrepresentation, were observed for 1p (25%), 3p (25%), 4p (14%), 9p (19%), 11q (28%), and 14q (31%). The presence of 3p, 11q or 14q deletions defines a genetic subset of neuroblastomas and contributes to the further genetic characterization of stage 3 and 4 tumors without MYCN amplification (MNA) and 1p deletion. The present study also provides additional evidence for a possible role of genes at 11q13 in neuroblastoma. In a few cases, 1p deletion or MNA detected by FISH or Southern blotting was not found by CGH, indicating that the use of a second, independent technique for evaluation of these genetic parameters is recommended. Genes Chromosomes Cancer 23:141–152, 1998. © 1998 Wiley-Liss, Inc.

Background and Methods The implications of the detection of residual disease after treatment of acute lymphoblastic leukemia (ALL) are unclear. We conducted a prospective study at 11 centers to determine the predictive value of the presence or absence of detectable residual disease at several points in time during the first six months after complete remission of childhood ALL had been induced. Junctional sequences of T-cell–receptor or immunoglobulin gene rearrangements were used as clonal markers of leukemic cells. Residual disease was quantitated with a competitive polymerase-chain-reaction (PCR) assay. Of 246 patients enrolled at diagnosis and treated with a uniform chemotherapy protocol, 178 were monitored for residual disease with one clone-specific probe (in 74 percent) or more than one probe (in 26 percent). The median follow-up period was 38 months. Results The presence or absence and level of residual leukemia were significantly correlated with the risk of early relapse at each of the times studi...