In soft tissue sarcomas, clonal rearrangement of chromosomes has been shown by cytogenetic analysis to be unique and specific for tumor types. The development of fluorescence in situ hybridization (FISH) has allowed detection of chromosomal rearrangements in the interphase nuclei isolated from paraffin-embedded tissues. Three kinds of translocations in the interphase nuclei that were isolated from 47 cases of soft tissue sarcomas were examined by FISH with chromosome-specific DNA probes of centromeric and total probes. Of 47 soft tissue sarcomas 42 (89.4%) revealed tumor-specific translocations by retrospective cytogenetic analysis. Translocation t(X;18) was detected in 25/28 synovial sarcomas; translocation t(11;22) in 5/6 Ewing's sarcomas and primitive neuroectodermal tumors (PNET); and translocation t(12;16) was found in 12/13 liposarcomas, including 10 myxoid and two round cell types as clonal chromosomal aberrations specific for both subtypes. Based on the cytogenetic analysis, Ewing's sarcoma is related closely with PNET as shown by MIC2-protein reactivity. Other cytogenetic findings of translocation t(12;16) indicate that round cell liposarcomas share chromosomal changes with myxoid liposarcomas, and further suggest that both tumor subtypes of liposarcoma may possess common precursor cells. FISH is a useful aid in determining the tumor type of soft tissue sarcomas with regard to histogenetic origin.
The interphase cytogenetics in formalin-fixed and paraffin-embedded gastric cancer tissues were examined by fluorescence in situ hybridization (FISH) with alpha-satellite DNA probes. Two gastric carcinoma cell lines, TMK-1 and MKN-28, were first analyzed cytogenetically. Of 25 TMK-1 cell karyotypes, chromosome 7 showed trisomy and chromosome 17 showed disomy in 18 cells. Most MKN-28 cells showed disomy of both chromosomes 7 and 17. Suspensions of singly isolated TMK-1 and MKN-7 cells were obtained from the cultured cells, and from paraffin-embedded tissue specimens fixed with formalin for 0, 1, 3 and 5 days obtained from xenotransplanted tumors in nude mice. The numbers of chromosomes 7 and 17 analyzed with the karyotypic preparations coincided well with those determined by FISH, even in the paraffin-embedded specimens. The number of tumor cells showing no signals, however, increased in the specimens after 5 days formalin fixation. In 10 surgically removed gastric carcinomas, the predominant signal number for chromosomes 7 and 17 in the cells of paraffin-embedded tissues was two (disomy), except in one papillary carcinoma, which was trisomic for chromosome 7. Large subpopulations (more than 20%) showing trisomy were found in four cases for chromosome 7 and in five cases for chromosome 17. A higher frequency of trisomy was found in well differentiated than in poorly differentiated carcinomas. These findings suggest that the FISH technique is a useful tool for detecting chromosomal aberrations in gastric adenocarcinoma cells, even in paraffin-embedded specimens, as long as the tissues are fixed with formalin for an appropriate time.
A 57-year-old female patient with synovial sarcoma in her right foot had a chromosome abnormality defined as translocation (X;18). The tumour was located in the subcutis, and histological investigation showed monophasic proliferation of oval to spindle-shaped cells with a fascicular arrangement lacking an epithelial component. Immunostaining disclosed no cytokeratin or epithelial membrane antigen in tumour cells. Karyotypic analysis revealed translocation (X;18) in addition to other nonspecific aberrations. Fluorescence in situ hybridization was carried out on paraffin-embedded tissue, using DNA probes for the centromeres of chromosomes X and 18 with whole chromosome painting probes for X and 18. The free nuclei showed two signals at a rate of 83-85% with the X and 18 centromeric probes, in contrast to three signals at a rate of 68-70% with the X and 18 painting probes.
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