Trisomy 8 as a nonrandom secondary change in myxoid liposarcoma

An overview on liposarcoma subtypes: Genetic alterations and recent advances in therapeutic strategies

Liposarcoma (LPS) is a rare malignancy of adipocytic differentiation. According to World Health Organization classification, LPS comprises of four principle subtypes Atypical lipomatous tumor/Well-differentiated liposarcoma (ATL/WDLPS), Dedifferentiated liposarcoma (WDLPS), Myxoid liposarcoma (MLPS), and Pleomorphic liposarcoma (PLPS). Each subtype can develop at any location and shows distinct clinical behavior and treatment sensitivity. ATL/ WDLPS subtype has a higher incidence rate, low recurrence, and is insensitive to radiation and chemotherapy. DDLPS is the focal progression of WDLPS, which is aggressive and highly metastasizing. MLPS is sensitive to radiation and chemotherapy, with a higher recurrence rate and metastasis. PLPS subtype is highly metastasizing, has a poor prognosis, and exhibiting higher recurrence rate. Initial histological analysis provides information for the characterization of LPS subtypes', further molecular and genetic analysis provides certain subtype specifications, such as gene amplifications and gene fusions. Such molecular genetic alterations will be useful as therapeutic targets in various cancers, including the LPS subtypes. A wide range of novel therapeutic agents based on genetic alterations that aim to target LPS subtypes specifically are under investigation. This review summarizes the LPS subtype classification, their molecular genetic characteristics, and the implications of genetic alterations in therapeutics.

Genetic characterization of intramuscular myxomas

Introduction: Intramuscular myxomas are benign tumors that are challenging to diagnose, especially on core needle biopsies. Acquired chromosomal aberrations and pathogenic variants in codon 201 or codon 227 in GNAS complex locus gene (GNAS) have been reported in these tumors. Here we present our genetic findings in a series of 22 intramuscular myxomas. Materials and methods: The tumors were investigated for the presence of acquired chromosomal aberrations using G-banding and karyotyping. Pathogenic variants in codon 201 or codon 227 of GNAS were assessed using direct cycle Sanger sequencing and Ion AmpliSeq Cancer Hotspot Panel v2 methodologies. Results: Eleven tumors carried chromosomal abnormalities. Six tumors had numerical, four had structural, and one had both numerical and structural chromosomal aberrations. Gains of chromosomes 7 and 8 were the most common abnormalities being found in five and four tumors respectively. Pathogenic variants in GNAS were detected in 19 myxomas (86%) with both methodologies. The detected pathogenic variants were p.R201H in nine cases (seven with abnormal and two with normal karyotypes), p.R201C in five cases, all with normal karyotypes, p.R201S in three cases (two with abnormal and one with normal karyotype), p.R201G in one case with a normal karyotype, and p.Q227E in one case with a normal karyotype. Conclusion: Firstly, our data indicate a possible association between chromosomal abnormalities and GNAS pathogenic variants in intramuscular myxomas. Secondly, the presence of the rare pathogenic variants R201S, p.R201G and p.Q227E in 26% (5 out of 19) of myxomas with GNAS pathogenic variants shows that methodologies designed to detect only the common "hotspot" of p.R201C and p.R201H will give false negative results. Finally, a comparison between Ion AmpliSeq Cancer Hotspot Panel v2 and direct cycle Sanger sequencing showed that direct cycle Sanger sequencing provides a quick, reliable, and relatively cheap method to detect GNAS pathogenic variants, matching even the most cutting-edge sequencing methods.

MDM2 amplification and fusion gene ss18-ssx in a poorly differentiated synovial sarcoma: A rare but puzzling conjunction

The detection of specific alterations by genetic analyses has been included in the diagnostic criterions of the World Health Organization's classification of soft tissues tumors since 2013. The presence of a SS18 rearrangement is pathognomonic of synovial sarcoma (SS). MDM2 amplification is strongly correlated to well-differentiated or dedifferentiated liposarcoma (DDLPS) in the context of sarcoma. We identified one case of poorly differentiated sarcoma harboring both SS18-SSX2 fusion and MDM2 amplification. The review of the literature showed high discrepancies, concerning the incidence of MDM2 amplification in SS: from 1.4% up to 40%. Our goal was to precisely determine the specific clinico-pathological features of this case and to estimate the frequency and characteristics of the association of SS18-SSX fusion/MDM2 amplification in sarcomas. We performed a retrospective and prospective study in 96 sarcomas, (56 SS and 40 DDLPS), using FISH and/or array-CGH to detect MDM2 amplification and SS18 rearrangement. None of the 96 cases presented both genetic alterations. Among the SS, only the index case (1/57: 1.7 %) presented the double anomaly. We concluded that MDM2 amplification in SS is a very rare event. The final diagnosis of the index case was a SS with SS18-SSX2 and MDM2 amplification as a secondary alteration. If the detection of MDM2 amplification is performed first in a poorly differentiated sarcoma, that may lead to not search other anomalies such as SS18 rearrangement and therefore to an erroneous diagnosis. This observation emphasizes the strong complementarity between histomorphology, immunohistochemistry and molecular studies in sarcoma diagnosis.

Cytogenetics and molecular genetics of myxoid soft-tissue sarcomas

Myxoid soft-tissue sarcomas represent a heterogeneous group of mesenchymal tumors characterized by a predominantly myxoid matrix, including myxoid liposarcoma (MLS), low-grade fibromyxoid sarcoma (LGFMS), extraskeletal myxoid chondrosarcoma (EMC), myxofibrosarcoma, myxoinflammatory fibroblastic sarcoma (MIFS), and myxoid dermatofibrosarcoma protuberans (DFSP). Cytogenetic and molecular genetic analyses have shown that many of these sarcomas are characterized by recurrent chromosomal translocations resulting in highly specific fusion genes (e.g., FUS-DDIT3 in MLS, FUS-CREB3L2 in LGFMS, EWSR1-NR4A3 in EMC, and COL1A1-PDGFB in myxoid DFSP). Moreover, recent molecular analysis has demonstrated a translocation t(1; 10)(p22; q24) resulting in transcriptional upregulation of FGF8 and NPM3 in MIFS. Most recently, the presence of TGFBR3 and MGEA5 rearrangements has been identified in a subset of MIFS. These genetic alterations can be utilized as an adjunct in diagnostically challenging cases. In contrast, most myxofibrosarcomas have complex karyotypes lacking specific genetic alterations. This paper focuses on the cytogenetic and molecular genetic findings of myxoid soft-tissue sarcomas as well as their clinicopathological characteristics.

Liposarcoma: molecular genetics and therapeutics

Sarcomas are a group of heterogeneous tumours with varying genetic basis. Cytogenetic abnormalities range from distinct genomic rearrangements such as pathognomonic translocation events and common chromosomal amplification or loss, to more complex rearrangements involving multiple chromosomes. The different subtypes of liposarcoma are spread across this spectrum and constitute an interesting tumour type for molecular review. This paper will outline molecular pathogenesis of the three main subtypes of liposarcoma: well-differentiated/dedifferentiated, myxoid/round cell, and pleomorphic liposarcoma. Both the molecular basis and future avenues for therapeutic intervention will be discussed.

Classification and pathology

Soft tissue tumors are a heterogeneous group of benign and malignant processes. Some are assumed to be reactive; others are clearly neoplastic. Because of their rarity, they frequently pose diagnostic problems for surgical pathologists. Accurate diagnosis of these tumors is enhanced by knowledge of the clinical features of the given lesions and, at times, by application of immunohistochemical and molecular techniques. In this article the lesions are described essentially in accordance with the World Health Organization classification.

Frequency and implications of chromosome 8 and 12 gains in Ewing sarcoma

Ewing sarcoma (ES) is the second most common primary malignant tumor of bone in children and young adolescents. Most ES contain a pathognomonic translocation t(11;22)(q24;q12) that is likely a pivotal event in the tumorigenesis of these neoplasms. Many ES also contain nonrandom, numerical chromosomal aberrations, the most common of which are trisomies 8 and 12. In this study we evaluated the hypothesis that these trisomies might occur during neoplastic progression and might be associated with differences in biologic behavior. We tested this hypothesis using a combined cytogenetic and dual color fluorescence in situ hybridization approach to determine chromosome 8 and 12 copy number in 52 ES. Relative gains, primarily trisomies, of chromosomes 8 and 12 were found in 24 (46%) and 17 (33%) cases, respectively. Trisomy 8 and trisomy 12 were independent events acquired in a flexible order during ES genetic progression. Our preliminary findings also suggest a higher frequency of trisomies 8 and 12 in relapses than in primary tumors. Prospective studies will be required to determine whether either trisomy is prognostic in newly-diagnosed ES.

Myxoid liposarcoma of the scalp: case report and literature review

Myxoid liposarcoma of the head and neck is an extremely rare entity. The scalp region represents a risk factor to the patient because the diagnosis is usually made late, and the surgeon must have a high index of suspicion for this entity because suctioning the tumor without taking a biopsy further delays an accurate diagnosis.

Ten years of the cytogenetics of soft tissue tumors

Recent cytogenetic and molecular genetic investigations in solid tumors in general, and in soft tissue tumors in particular, have provided us with a wealth of information. We have gained new insights in how tumors may arise, and some soft tissue tumors besides their identification by pathology now also have a genetic identity. This genetic identity is defined by: specific chromosome changes and by molecular changes related to the chromosome anomalies. However, much work remains to be done. In soft tissues as in other solid tumors many tumor types await the first or more extensive chromosome investigation, and in those in which nonrandom, especially simple chromosome changes emerge, molecular studies are to be undertaken starting from the breakpoints. Those tumors that seem to deviate chromosomally or molecularly from the expected, because of already established genetic changes, must be more thoroughly investigated by both pathologists and geneticists. The same accounts for the molecular investigation of chromosomally normal tumors known to show subtypes with specific chromosomal changes: e.g. lipoma, leiomyoma.

Fibrosarcoma versus cellular fibroma of the ovary: a comparative study of their proliferative activity and chromosome aberrations using MIB-1 immunostaining, DNA flow cytometry, and fluorescence in situ hybridization

We retrospectively analyzed the proliferative activity and the centromeric copy number of chromosomes 8, 12, and 17 in three cases of fibrosarcoma and eight cases of cellular fibroma of the ovary using MIB-1 immunostaining, DNA flow cytometry, and fluorescence in situ hybridization (FISH) on paraffin-embedded tissue specimens. In our study, both the MIB-1 labeling index (LI) and the proliferative index (% of cells in S + G2 + M phase) in fibrosarcomas were higher than those in cellular fibromas. The FISH analysis demonstrated the sole abnormality of a gain of trisomy 12 cells in all eight cases of cellular fibroma. Both a gain of trisomy 12 cells and a gain of tetrasomy 12 cells were observed in one case of fibrosarcoma. A gain of trisomy 8 cells was observed in all two fibrosarcomas in which signals were detected. By contrast, neither a gain of trisomy 8 cells nor a gain of tetrasomy 12 cells was observed in any of the eight cases of cellular fibroma. Chromosome 17 showed disomy in all eleven cases. On the basis of these findings, a gain of trisomy 8 cells is therefore considered to be an adequately effective marker to distinguish between cellular fibroma and fibrosarcoma of the ovary, and it may also be related to the proliferative activity of fibrosarcoma of the ovary.

Cytogenetic analysis of a case of myxoid liposarcoma with cartilaginous differentiation

The cytogenetic analysis of a patient with a myxoid liposarcoma exhibiting cartilaginous differentiation is presented. A complex translocation involving chromosome 12, 16, and 19 was found, instead of the t(12;16), specific for myxoid liposarcoma. The involvement of 19q13 in a tumor with cartilaginous differentiation, and the assignment of TGF beta 1 to 19q13.1-13.2, which appears to play a role in the formation of bone and cartilage, suggest a possible relation between both.

Lipomatous tumours of soft tissues: an update

This review summarizes the clinicopathological features of recently characterized variants of lipomatous tumours of soft tissue, attempts to deal with some difficult conceptual issues relating to adipocytic neoplasms and aims to provide an update on cytogenetic aspects of fatty tumours. Myolipoma is a rare benign neoplasm, occurring most frequently in adults in the deep soft tissue of the abdomen or retroperitoneum, and is composed of irregularly admixed mature adipose and smooth muscle tissues. Chondroid lipoma represents an unusual benign lesion occurring mainly in adult females subcutaneously or in deep soft tissue; it is easily mistaken for myxoid liposarcoma or extraskeletal myxoid chondrosarcoma. Spindle-cell liposarcoma is a variant of well-differentiated liposarcoma quite commonly found in subcutaneous tissue of the shoulder region and upper limbs and is composed of relatively bland-appearing spindle cells mixed with a well-differentiated liposarcomatous component. Recently there has been considerable debate about classification of lipomatous tumours. The term atypical lipoma was proposed for a group of well-differentiated non-metastasizing liposarcomas arising in surgically amenable soft tissues and for deep-seated atypical adipocytic neoplasms that show variation in adipocytic size and atypical stromal cells but lack lipoblasts. However, these neoplasms recur repeatedly and may dedifferentiate and thereby acquire metastatic potential. We use the diagnosis atypical lipoma with caution and propose to use the terms well-differentiated liposarcoma and atypical lipoma interchangeably. The relationship between myxoid and round-cell liposarcoma, which constitutes the morphological spectrum of a single entity, has been clarified but there remain considerable problems in defining likely clinical behaviour. The recent advances in cytogenetic characterization and classification of lipomatous tumours, which is already proving to be of diagnostic importance, are reviewed, and the genetic importance of the distinct chromosomal translocation in myxoid/round cell liposarcoma is briefly discussed.

Trisomy 8 in alveolar soft part sarcoma

Cytogenetic studies were performed on an alveolar soft part sarcoma of a 6-year-old boy. An extra chromosome 8 was present in 26 of 28 metaphases analyzed.

Trisomy 8 and 18 as frequent clonal and single-cell aberrations in 185 primary breast carcinomas

For cytogenetic investigations short-term cultures of 185 breast carcinomas (135 invasive ductal, 21 invasive lobular, 12 invasive ductal with intraductal components, seven heterogeneous, six intraductal, four invasive ductal and lobular) were prepared. Cytogenetic examinations revealed clonal abnormalities in 39 cases with a predominance of simple numerical chromosome changes, i.e., trisomies of chromosomes 7, 8, and 18. One hundred forty-six tumors did not show clonal abnormalities, but single-cell aberrations other than monosomies occurred in 79 of these tumors. Compared to cells of epithelial hyperplasia of the breast, amniotic fluid cells, and cells from pleomorphic adenomas cultivated using the same medium, the frequency of single-cell trisomies was significantly higher. Trisomy 8 was not only found as a clonal aberration in 10 cases but was also the most frequent non-clonal aberration. Trisomy 7 and 18 were also frequent clonal as well as non-clonal cytogenetic deviations.

Deletion 6q in three cases of mixed-type liposarcoma in addition to t(12;16)(q13;p11)

We report the cytogenetic findings in three mixed liposarcoma following short-term cultures. During the course of cytogenetic investigation of various types of liposarcomas, we observed an interstitial deletion of the long arm of chromosome 6 together with the translocation (12;16)(q13;p11) in three tumors. Translocation (12;16) is associated with myxoid and mixed (myxoid/round cell) liposarcomas, although deletion of chromosome 6 has been observed in only a few of these tumors. Our findings suggest that del(6), as an additional change in myxoid liposarcoma, is probably related to tumor progression.

Cytogenetics of tumors of soft tissue and bone. Implication for pathology

Pathologists should be aware of the existence of diagnostically useful chromosomal rearrangements in several soft tissue and bone tumors. They include rearrangement of 8q12 in lipoblastomas, ring chromosomes in atypical lipomas, ring and giant marker chromosomes in well differentiated liposarcomas, t(12;16)(q13;p11) in myxoid liposarcomas, rearrangement of 7p21-22 in low-grade endometrial stromal sarcomas, t(2;13)(q37;q14) in alveolar rhabdomyosarcomas, t(X;18)(p11.2;q11.2) in synovial sarcomas, t(12;22) (q13;q13) in clear cell sarcomas, t(11;22)(q24;q12) in Ewing's sarcomas and peripheral neuroepitheliomas, and t(9;22)(q21-31;q11-12) in extraskeletal myxoid chondrosarcomas.

Myxoid liposarcoma. Experience with chemotherapy

BACKGROUND

Myxoid liposarcoma (ML) is the most common type of liposarcoma. It has been classified as an intermediate grade tumor with a definite metastatic potential but a relatively indolent natural history. Little is known about its sensitivity to chemotherapy.

METHOD

The authors reviewed their experience with chemotherapy in ML from 1986 to 1992. The patient population was identified through a search of the database maintained by the Department of Melanoma-Sarcoma Medical Oncology of the M.D. Anderson Cancer Center.

RESULTS

Forty-four patients each with a histologically confirmed diagnosis of ML were identified. Twenty-one were treated with chemotherapy. The median age was 45 years (31-69 years); there were 14 men and 7 women. The ML in 19 patients was in the lower extremity, one in the head and neck, and one pelvic. The median size of the primary tumor was 15 cm (range, 7-48 cm) in maximum dimension. Of the 18 patients who received doxorubicin- and dacarbazine-based chemotherapy as a frontline regimen [median of 3 (2-9) cycles] and were evaluable for response, 8 (1 completed response, 7 partial responses) achieved an objective response (44%, 95% confidence interval 21-67%). Two of the remaining three patients who were also treated with a similar regimen were not evaluable for response (one received chemotherapy postoperatively, and the other received concomitant radiation and doxorubicin), and the third patient received ifosfamide as frontline chemotherapy because of a significant cardiac history. Seven patients received chemotherapy in the neoadjuvant setting, 13 for recurrent or metastatic disease, and 1 postoperatively after complete tumor resection. At the last follow-up, 10 patients were alive with no evidence of disease, 3 were alive with disease, and 8 had died. The median follow-up was 51 months (range, 6-199 months) from diagnosis.

CONCLUSION

The authors conclude that doxorubicin- and dacarbazine-based chemotherapy is effective in the treatment of ML.

Hibernomas are characterized by rearrangements of chromosome bands 11q13-21

Cytogenetic analysis revealed structural rearrangements of 11q13-21 in 9 lipogenic tumors--4 hibernomas, 4 typical lipomas and 1 mixed myxoid and well-differentiated liposarcoma. Two hibernomas and all lipomas simultaneously showed aberrations attributable to previously recognized cytogenetic subgroups among benign adipose tissue tumors, i.e., supernumerary ring chromosomes or rearrangements of 6p, 12q13-15, or 13q. The sole anomaly in the liposarcoma was a 4-way translocation t(9;11;22;12)(q21;q13;q11;q13), an aberration that has not previously been detected in either myxoid or well-differentiated liposarcomas. Together with our 4 cases, a total of 7 cytogenetically aberrant hibernomas have been reported. Five tumors have shown rearrangements of 11q13 and 2 of 11q21, indicating that this segment of chromosome 11 harbors one or more genes of importance in hibernoma development. Rearrangements of 11q13-21 also appear to be frequent in typical lipomas; a total of 8 typical lipomas with 11q13-21 changes have been described, including those in our series. In all but 1 however, breakpoints were also found in 6p, 12q13-15, or 13q.

Cytogenetic aberrations in 188 benign and borderline adipose tissue tumors

Chromosome studies of lipomas have revealed an extensive cytogenetic heterogeneity. To investigate the frequencies of previously recognized cytogenetic subgroups and to find out if more recurrent rearrangements can be identified, we have analyzed cytogenetically short-term tissue cultures of 237 samples from 188 adipose tissue tumors obtained from 142 patients. Only one of 58 tumors from 18 patients with multiple lipomas (more than two tumors) had karyotypic changes. Among the sporadic lipomas, 20 tumors had supernumerary ring chromosomes of unknown origin, 55 had different aberrations involving chromosome segment 12q13-15, 11 had changes of 6p or chromosome 13, but no rings or 12q13-15 changes, and 14 had various other aberrations. Ring chromosomes were found in all cytogenetically abnormal lipomas histologically classified as atypical and in nine tumors classified as typical lipoma or spindle cell lipoma. Recombinations between 12q13-15 and a few other bands or segments were seen more than once: 3q27-28 (15 tumors), 2p22-24 and 2q35 (four tumors), 1p32-34 and 13q12-14 (three tumors), and 5q33 (two tumors). Recombinations of 12q13-15 with 2q35 and 13q12-14 have not been described before. Of eight tumors with chromosome 13 aberrations, five had loss of 13q material. Aberrations of 12q13-15, 6p, and/or chromosome 13 were found simultaneously in nine tumors. Two to four samples from the same tumor were investigated in 29 tumors with clonal aberrations. Thirteen of these tumors displayed clonal evolution, also noted in another 17 tumors in which only one sample had been investigated. Thus clonal evolution occurred in 30% of the tumors and was particularly frequent in atypical lipomas.

Aberrations of chromosome 22 and polysomy of chromosome 8 as non-random changes in clear cell sarcoma

Cytogenetic analysis was performed on a primary tumor and a metastatic lesion of a clear cell sarcoma of tendons and aponeuroses (CCS), a rare soft tissue neoplasm of uncertain histopathologic origin. Clonal chromosomal abnormalities resulting in two related clones were found in both tumors. The karyotype was near-triploid with several structural and numerical changes, comprising a der(15;22) (q10;q10). Including the present case, 14 of 15 cases of CCS have had structural or numerical aberrations of chromosome 22 and nine of them (65%) displayed a similar or identical t(12;22)(q13-14;q12-13). Our findings suggest that in the absence of specific t(12;22), other abnormalities of chromosome 22 may be significant. In addition, increased doses of chromosome 8 found in 70% of the tumors strongly suggest a significant role for this chromosome in the development of clear cell sarcoma.

A case report of fibrolipoma with t(12;16)(q13;q24)

Chromosomal analysis of a fibrolipoma of the shoulder of a 55-year-old man showed the following abnormal complement: 46,XY,t(12;16)(q13;q24). Comparison with two previously characterized fibrolipomas showed abnormalities reportedly observed in "classic lipoma." A unique or distinguishing anomaly for fibrolipoma was not detected. Therefore, fibrolipoma appears to be distinct histologically but not cytogenetically.

Aberrations of chromosome segment 12q13-15 characterize a subgroup of hemangiopericytomas

BACKGROUND

In later years, several characteristic acquired chromosomal aberrations have been identified in mesenchymal tumors. Many of these aberrations, either alone or with histopathologic and clinical data, are useful in diagnosis. The cytogenetic profile of hemangiopericytomas has been poorly investigated.

METHODS

Short-term cultures from four spindle cell tumors were cytogenetically analyzed.

RESULTS

Clonal acquired chromosome aberrations were found in three of the four tumors: inv(12) (q14q24) in a malignant hemangiopericytoma, a supernumerary der(3)t(3;12) (p21-23;q13-15) in a benign hemangiopericytoma, and t(6;12;19) (p21;q13;p13) in a spindle cell sarcoma that was histologically a malignant hemangiopericytoma or a synovial sarcoma. The fourth tumor, a malignant hemangiopericytoma, had a normal karyotype. The tumors with inv(12) and t(6;12;19) had subclones with trisomy 5 in addition to the structural changes.

CONCLUSIONS

The current findings and the literature data indicate that a subgroup of hemangiopericytomas is characterized by rearrangement of chromosome segment 12q13-15.

Translocation t(12;22)(q13;q12.2-12.3) in a clear cell sarcoma of tendons and aponeuroses

Cytogenetic analysis of a short-term culture from a clear cell sarcoma revealed a complex karyotype with the mainline of 49,XY,t(7;18)(p11.2;q21.3), +der(7)t(7;18)(p11.2;q21.3), +8, +der (8;17)(q10;q10),t(12;22)(q13;q12.2-12.3),add(13)(p13). An apparently identical translocation t(12;22) has been described recently in four clear cell sarcomas, indicating that this constitutes a primary cytogenetic change specific for this type of tumor. In our case, the breakpoint on chromosome 22 could be assigned to band 22q12.2 or 22q12.3. Together with the present case, trisomy or tetrasomy 8 has been found in six of nine clear cell sarcomas, suggesting that, as in Ewing's sarcoma and myxoid liposarcoma, trisomy/tetrasomy 8 represents a nonrandom secondary aberration. We conclude that the finding of the specific translocation t(12;22) may prove to be an important marker in the differential diagnosis of clear cell sarcoma from some other soft tissue sarcomas and malignant melanoma.

Comparative cytogenetic and DNA flow cytometric analysis of 150 bone and soft-tissue tumors

Samples from 48 benign and 102 malignant bone and soft-tissue tumors were analyzed cytogenetically and by DNA flow cytometry. Clonal chromosome abnormalities were found in 82 tumors and normal karyotypes in 68; 61 tumors were DNA-non-diploid and 89 were diploid. The cytogenetically abnormal tumors were used for comparison between the 2 types of investigation; 45 of these tumors were DNA-diploid and 37 were DNA-non-diploid. There was, with few exceptions, good correspondence between the quantitative estimates of genomic changes by the 2 methods, indicating that the cells cytogenetically analyzed from short-term cultures are representative of the in vivo cell populations. Discrepancies were primarily found in cases with indexes above 1.5, in which the DNA index was higher than the chromosome index. The chromosome analysis suggested that skewed stemline (G0/G1) peaks in the diploid region in DNA histograms indicate the presence of cell populations with small net quantitative genomic changes, although not all such populations were detected by DNA flow cytometric analysis. The view that one of the peaks in bimodal stemline DNA histograms with narrow peaks represents a non-diploid cell population was also corroborated. On average, the cell populations giving rise to double stemlines in DNA histograms showed quantitatively larger genomic changes than those that gave rise to broad or skewed diploid G0/G1 peaks. The findings indicate that these histogram profiles are not artifactual but reflect chromosomal changes in the tumor parenchyma.

Rearrangement of band q13 on both chromosomes 12 in a periosteal chondroma

Cytogenetic analysis of a recurrent periosteal chondroma revealed nonreciprocal translocations of both chromosomal segments 12q13-->qter, from one chromosome 12 to 7q32 and from the homologous chromosome 12 to 16q22. The remaining parts of the two chromosomes 12 formed a dicentric chromosome. This is the second reported chondroma with a 12q13-15 rearrangement, and changes of this chromosome region consequently seem to be nonrandom occurrences in chondromas.

Trisomy 8 as a recurrent clonal abnormality in breast cancer?

The results of cytogenetic investigations on one benign and 15 malignant breast tumors are described. Trisomy 7, 8, 18, and 21 and monosomy X occurred as clonal numerical aberrations, and inv(7)(q21q31) and t(4;12)(q21;p13) occurred as clonal structural aberrations. Only trisomy 8 was a recurrent karyotypic abnormality, however. Thus, we assumed that trisomy 8 as an early genetic change characterizes a subtype of ductal breast carcinomas.

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

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.

t(12;22)(q13;q13) and trisomy 8 are nonrandom aberrations in clear-cell sarcoma

We report a case of clear-cell sarcoma with a t(12;22)(q13;q13) and multiple copies of chromosome 8 in addition to other abnormalities. An identical or similar translocation has previously been reported in this type of tumor, suggesting that the t(12;22) is a primary cytogenetic change in the pathogenesis of a subset of clear-cell sarcomas. In addition, the presence of extra copies of chromosome 8, commonly noted in our case and others, suggests that it represents a nonrandom secondary change in these tumors.

Significance of both numerical and structural chromosomal abnormalities in clear cell sarcoma

We analyzed cytogenetically two cases of clear cell sarcoma. The t(12;22)(q13;q13) hypothesized to be characteristic of clear cell sarcoma was detected in one of the two cases. Although this translocation was not observed in the other case; trisomy of chromosome 22 was, as were other numerical abnormalities. This latter observation has also been described in other reported studies of clear cell sarcoma. These findings confirm the nonrandomness of t(12;22)(q13;q13) in clear cell sarcoma, but also suggest that in its absence other abnormalities of chromosome 22 are significant. Trisomy 8, noted in both cases we report, as well as in previous studies, also appears to play an important role in clear cell sarcoma.

Chromosome abnormalities in liposarcomas

We performed a cytogenetic study of short-term cultures from fresh surgical specimens obtained from four patients with liposarcoma. Myxoid liposarcomas (cases 1-3) were associated with a specific translocation between chromosomes 12 and 16. Trisomy 8, a nonrandom secondary aberration in myxoid liposarcoma, was observed in the third case as the only additional change. Round cell liposarcoma (case 4) showed complex chromosomal aberrations affecting chromosomes 1, 2, 5, 6, 7, 13, 14, 17, 19, and 22. Neither band 12q13 nor 16p11 was visibly rearranged. Three subgroups of liposarcomas are proposed. The first group is characterized by t(12;16)(q13;p11), the second group by ring chromosomes, telomeric associations, and giant markers, and the last by complex numerical and structural aberrations.

Rearrangement of the transcription factor gene CHOP in myxoid liposarcomas with t(12;16)(q13;p11)

Most myxoid liposarcomas (MLS) are characterized cytogenetically by a t(12;16)(q13;p11). It is reasonable to assume that this translocation corresponds to the consistent rearrangement of one or two genes in 12q13 and/or 16p11, and that the loci thus affected are important in the normal control of fat cell differentiation and proliferation. We have used Southern blot technique to test whether a gene of the CCAAT/enhancer binding protein (C/EBP) family, CHOP, which maps to 12q13 and is assumed to be involved in adipocyte differentiation, could be the 12q gene in question. Using a cDNA probe that spans the CHOP coding region, we detected one rearranged and one wild type allele in nine of nine MLS with t(12;16). Using PCR generated, site-specific probes corresponding to the non-coding exons 1 and 2 and intron 2 of CHOP, rearrangements in five of seven tumors mapped to the 2.4 and 1.6 kbp PstI fragments that contain the first two exons and introns of the gene and the upstream promoter region. In contrast to the findings in MLS, no tumor without a t(12;16) exhibited aberrant CHOP restriction digest patterns. These tumors included one highly differentiated liposarcoma with abnormal karyotype but no involvement of 12q13, seven lipomas with various cytogenetic aberrations of 12q13-15, two uterine leiomyomas with t(12;14) (q14-15;q23-24), and one hemangiopericytoma and one chondroma, both of which also had 12q13 changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Supernumerary ring chromosomes in five bone and soft tissue tumors of low or borderline malignancy

Five tumors (two myxoid malignant fibrous histiocytoma, two dermatofibrosarcoma protuberans, and one parosteal osteosarcoma) with ring chromosomes as the sole cytogenetic anomaly or as the only structural rearrangement were observed in a series of 60 karyotypically abnormal, nonlipogenic bone and soft tissue tumors (BST). All five tumors were of borderline or low malignancy. These findings support the suggestion that supernumerary ring chromosomes as the sole structural chromosomal aberration are not associated with any particular histopathologic diagnosis but may characterize a group of BST of borderline or low malignancy.

Cytogenetic findings in liposarcoma correlate with histopathologic subtypes

The cytogenetic findings in 31 liposarcomas from 26 patients are reported. Four other tumors did not grow. Three histologic types are represented in this analysis. The well-differentiated liposarcomas were characterized by telomeric associations, large marker chromosomes and ring chromosomes, and in some cases, double minutes. The pleomorphic liposarcomas contained very high clonal chromosomal numbers with near-tetraploid modes and numerous variable, often unidentifiable, chromosomal abnormalities. The myxoid liposarcomas were characterized primarily by a t(12;16)(q13;p11) as the sole abnormality or additional changes. These results indicate that cytogenetic findings may provide a new criterion, not only for establishing the diagnosis of liposarcoma, but also for differentiating confusing histologic types of liposarcoma and these lesions from other types of sarcomas.