Cytogenetic findings in pediatric adipose tumors: Consistent rearrangement of chromosome 8 in lipoblastoma

Department of Pathology, Brigham and Women's Hospital, Boston, MA 02115.
Genes Chromosomes and Cancer (Impact Factor: 4.04). 01/1993; 6(1):24-9. DOI: 10.1002/gcc.2870060106
Source: PubMed


Characteristic cytogenetic aberrations have been reported in adult lipomas and liposarcomas, but few karyotypes have been reported for pediatric adipose neoplasms. In this report we describe a consistent rearrangement, der(8)(pter-->q13::q24.1-->qter), in 2 of 3 lipoblastomas. A similar der(8) was present in the only other published lipoblastoma karyotype, but this der(8) has not been reported in lipomas, liposarcomas, or nonadipose solid tumors. We investigated the potential specificity of der(8)(pter-->q13::q24.1-->qter) by karyotyping an unselected series of nonlipoblastoma adipose tumors in children and young adults. The series included 14 lipomas, 2 atypical lipomas ("well-differentiated liposarcomas"), and 2 angiomyolipomas; der(8) was not found in any tumor from this series. Three lipomas, however, contained rearrangements in the region of chromosome band 12q14, as has been described frequently in adult lipomas. Because clinical features in lipoblastoma can mimic those in liposarcoma, recognition of der(8)(pter-->q13::q24.1--qter) is of potential diagnostic relevance.

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    ABSTRACT: Lipoblastomas are rare soft tissue tumors that occur primarily in young children. They typically contain variably differentiated adipocytes, primitive mesen- chymal cells, myxoid matrix, and fibrous trabeculae. Abnormalities in chromosome 8, leading to rear- rangements of the PLAG1 gene, were demonstrated recently in four lipoblastomas. In the present report, we determine the frequency of PLAG1 alterations in 16 lipoblastomas from children aged 13 years or younger, and we also evaluate the stages of lipoblas- toma differentiation at which PLAG1 genomic alter- ations are found. Eleven lipoblastomas (69%), includ- ing those with either classic or lipoma-like histology, had rearrangements of the 8q12 PLAG1 region. An- other three lipoblastomas had polysomy for chromo- some 8 in the absence of PLAG1 rearrangement. Only two cases (13%) lacked a chromosome 8 abnormality. Notably, the lipoblastomas with chromosome 8 poly- somy had up to five copies of chromosome 8 as an isolated cytogenetic finding in an otherwise diploid cell. We also demonstrate that PLAG1 alterations are found in a spectrum of mesenchymal cell types in lipoblastomas, including lipoblasts, mature adipo- cytes, primitive mesenchymal cells, and fibroblast- like cells. This finding is consistent with neoplastic origin in a primitive mesenchymal precursor and with variable differentiation to a mature adipocyte end-point. Hence, our studies provide biological val- idation for the clinical observation that lipoblastomas can evolve into mature, lipoma-like, lesions. They also suggest that PLAG1 dosage alterations caused by polysomy 8 might represent an alternative oncogenic mechanism in lipoblastoma. (Am J Pathol 2001, 159:955-962)
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    ABSTRACT: We have karyotyped eight sporadic osteocartilaginous exostoses (OCE), a tumor type not characterized cytogenetically before. Five tumors had only normal karyotypes, whereas three displayed the following abnormal karyotypes: 46,XY,del(8)(q24.1); 46,XX,del(8)(q22), t(8;14)(q24.1;q32); and 46,XY,der(8)t(1;8)(q21;q24),inv(12)(p11q13). All three aberrant cases thus had structural rearrangements leading to loss of the distal part of 8q. This is of particular interest because multiple OCE are part of the disease phenotype in patients with the autosomal dominant tricho-rhino-phalangeal syndrome type II (TRP II), many of whom have constitutional loss of genetic material from 8q24.1. We hypothesis that band 8q24.1 harbors a tumor suppressor gene, the homozygous inactivation of which is important in the genesis of both inherited and sporadic OCE. In the familial form, i.e., in TRP II, loss or functional inactivation of one allele is inherited and only the second mutation is due to a somatic event, whereas both mutations are somatic in the sporadic forms. This hypothesis can be tested by analysis of sporadic and inherited OCE for homozygous loss of 8q24 material with molecular genetic techniques.
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