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

Genomic and transcriptomic features of dermatofibrosarcoma protuberans: Unusual chromosomal origin of the COL1A1-PDGFB fusion gene and synergistic effects of amplified regions in tumor development

The dermatofibrosarcoma protuberans family of tumors (DPFT) comprises cutaneous soft tissue neoplasms associated with aberrant PDGFBR signaling, typically through a COL1A1-PDGFB fusion. The aim of the present study was to obtain a better understanding of the chromosomal origin of this fusion and to assess the spectrum of secondary mutations at the chromosome and nucleotide levels. We thus investigated 42 tumor samples from 35 patients using chromosome banding, fluorescence in situ hybridization, single nucleotide polymorphism arrays, and/or massively parallel sequencing (gene panel, whole exome and transcriptome sequencing) methods. We confirmed the age-associated differences in the origin of the COL1A1-PDGFB fusion and could show that it in most cases must arise after DNA synthesis, i.e., in the S or G2 phase of the cell cycle. Whereas there was a non-random pattern of secondary chromosomal rearrangements, single nucleotide variants seem to have little impact on tumor progression. No clear genomic differences between low-grade and high-grade DPFT were found, but the number of chromosomes and chromosomal imbalances as well as the frequency of 9p deletions all tended to be greater among the latter. Gene expression profiling of tumors with COL1A1-PDGFB fusions associated with unbalanced translocations or ring chromosomes identified several transcriptionally up-regulated genes in the amplified regions of chromosomes 17 and 22, including TBX2, PRKCA, MSI2, SOX9, SOX10, and PRAME.

Building through breaking: the development of cancer neochromosomes

In this issue of Cancer Cell, Garsed and colleagues combine chromosome flow sorting and deep sequencing to characterize the structure of oncogene-containing neochromosomes in liposarcoma and provide evidence that they are generated by a combination of multiple dynamic and destructive processes.

Immunohistochemical analysis of MDM2 and CDK4 distinguishes low-grade osteosarcoma from benign mimics

Parosteal osteosarcoma and low-grade central osteosarcoma are two types of low-grade osteosarcoma that show similar clinical behaviors, histological features, and genetic background (ie, amplified sequences of 12q13-15, including MDM2 and CDK4). Low-grade osteosarcoma is often confused with benign lesions, and ancillary techniques to enhance diagnostic accuracy have been awaited. This study explores the use of MDM2 and CDK4 immunohistochemistry for the histological diagnosis of low-grade osteosarcoma. We studied 23 cases of low-grade osteosarcoma from 21 patients (parosteal osteosarcoma (n=14), low-grade central osteosarcoma (n=9)) and 40 cases of benign histological mimics (myositis ossificans (n=11), fibrous dysplasia (n=14), osteochondroma (n=6), desmoplastic fibroma (n=1), florid reactive periostitis (n=4), Nora's lesion (n=3), and turret exostosis (n=1)). Low-grade osteosarcoma labeled for MDM2 in 16 cases (70%) and for CDK4 in 20 cases (87%). All low-grade osteosarcomas expressed one or both markers (100%), with 13 cases (57%) expressing both. Staining pattern was diffuse in most cases, and the majority expressed moderate or strong intensity for either antibody. MDM2/CDK4 immunostaining was shown irrespective of low-grade osteosarcoma histological subtype. In contrast, only 1 Nora's lesion out of the 40 miscellaneous benign processes showed immunoreactivity for MDM2 or CDK4. The combination of these two markers thus shows 100% sensitivity and 97.5% specificity for the diagnosis of low-grade osteosarcoma. MDM2 and CDK4 immunostains therefore reliably distinguish low-grade osteosarcoma from benign histological mimics, and their combination may serve as a useful adjunct in this difficult differential diagnosis.

Chromosome analysis and molecular cytogenetic investigations of an epithelioid hemangioendothelioma

Epithelioid hemangioendothelioma is a rare, well-differentiated endothelial tumor with a wide spectrum of clinical behavior and for which genetic data are extremely limited. We present a case of an epithelioid hemangioendothelioma in a 22-year-old male, which was analyzed with multiple cytogenetic approaches. Conventional cytogenetic analysis detected structural abnormalities of 11q13 and 11q14, rings, and marker chromosomes. Multi-color FISH (mFISH) and high-resolution multi-color banding (mBAND) analyses demonstrated that the aberrations of chromosome 11 were deletions and that the ring and marker chromosomes consisted of 12(q14 approximately q21) material. Comparative genomic hybridization (CGH) analysis revealed gains of 11(q13 approximately q14) and 12(q11 approximately q21), loss of 11(q21 approximately qter), and 2 amplicons at 12(q12 approximately q13) and 12(q14 approximately q21). Our data indicate that a subset of epithelioid hemangioendotheliomas may be characterized by complex rearrangements involving deletions and gains of 11q and 12q amplifications. The present case also shows that, in order to describe and understand such complex chromosome aberrations, chromosome analysis must be complemented with several molecular cytogenetic techniques.

Genomic profiling of bone and soft tissue tumors with supernumerary ring chromosomes using tiling resolution bacterial artificial chromosome microarrays

Ring chromosomes and/or giant marker chromosomes have been observed in a variety of human tumor types, but they are particularly common in a subgroup of mesenchymal tumors of low-grade or borderline malignancy. These rings and markers have been shown to contain amplified material predominantly from 12q13-15, but also sequences from other chromosomes. Such amplified sequences were mapped in detail by genome-wide array comparative genomic hybridization in ring-containing tumor samples from soft tissue (n = 15) and bone (n = 6), using tiling resolution microarrays, encompassing 32 433 bacterial artificial chromosome clones. The DNA copy number profiles revealed multiple amplification targets, in many cases highly discontinuous, leading to delineation of large numbers of very small amplicons. A total number of 356 (median size: 0.64 Mb) amplicons were seen in the soft tissue tumors and 90 (median size: 1.19 Mb) in the bone tumors. Notably, more than 40% of all amplicons in both soft tissue and bone tumors were mapped to chromosome 12, and at least one of the previously reported recurrent amplifications in 12q13.3-14.1 and 12q15.1, including SAS and CDK4, and MDM2, respectively, were present in 85% of the soft tissue tumors and in all of the bone tumors. Although chromosome 12 was the only chromosome displaying recurrent amplification in the bone tumors, the soft tissue tumors frequently showed recurrent amplicons mapping to other chromosomes, that is, 1p32, 1q23-24, 3p11-12, 6q24-25 and 20q11-12. Of particular interest, amplicons containing genes involved in the c-jun NH2-terminal kinase/mitogen-activated protein kinase pathway, that is, JUN in 1p32 and MAP3K7IP2 (TAB2) in 6q24-25, were found to be independently amplified in eight of 11 cases with 12q amplification, providing strong support for the notion that aberrant expression of this pathway is an important step in the dedifferentiation of liposarcomas.

Local recurrence of myxofibrosarcoma is associated with increase in tumour grade and cytogenetic aberrations, suggesting a multistep tumour progression model

Myxofibrosarcoma is one of the most frequent soft tissue tumours in elderly patients, mostly arising in the extremities. Grade I lesions are only locally aggressive whereas grade II and grade III lesions have metastatic potential. The differential diagnosis contains several other (benign) myxoid soft tissue tumours. A number of sarcomas are characterised by specific cytogenetic aberrations, giving not only insight in their biological pathways; they also serve as molecular markers in difficult diagnoses. Cytogenetic data on myxofibrosarcoma are scarce with only few isolated cases described in the literature. No specific chromosomal aberrations have been detected so far. Moreover, molecular pathways in tumorigenesis and progression of myxofibrosarcoma are barely understood. We studied the clinicopathologic data and karyotypes of 32 myxofibrosarcomas using conventional banding and multicolour COmbined Binary RAtio labelling fluorescence in situ hybridisation technique. We included eight grade I, eight grade II and 16 grade III lesions. In all, 22 were primary tumours, nine were local recurrences and one a lymph node metastasis. The myxofibrosarcomas showed equal sex distribution, were mostly located at the extremities with two thirds deep-seated and had an average age of occurrence of 66 years. We found normal karyotypes in eight cases and clonal beside nonclonal aberrations in 22 cases. Complex cytogenetic anomalies were found in all grades. However, no tumour-specific chromosomal abnormalities could be withdrawn. Local recurrences showed increase in grade compared to their primary lesions. Interestingly, these recurrences showed more complex cytogenetic aberrations. Increase in grade seems to parallel increase in cytogenetic aberrations and malignant potential. Since the chromosomal aberrations found were not tumour type specific, they seem to be rather the result of secondary events in tumour progression and tumour genetic instability. Based on these findings, we suggest that tumorigenesis of myxofibrosarcoma is mainly a multistep genetic process, probably ruled by genetic instability caused by targeted checkpoint genes.

Dedifferentiated parosteal osteosarcoma: The experience of the Rizzoli Institute

BACKGROUND

Dedifferentiated parosteal osteosarcoma (DPOS) is a variant of osteosarcoma in which a high-grade sarcoma coexists with a conventional parosteal osteosarcoma (c-POS), either at presentation (synchronous type) or at the time of recurrence (metachronous type). Only approximately 60 patients have been reported in the literature. The objective of this study was to analyze the clinicopathologic and radiographic features of a relatively large number of patients with DPOS in an attempt to define further the histologic and biologic behavior of this rare entity.

METHODS

In a series of 120 patients with parosteal osteosarcoma who were seen at the Rizzoli Institute from 1958 to 2000, the authors identified 29 patients who were diagnosed with DPOS. The authors reviewed the clinical and radiologic features, histologic sections, treatments, and outcomes in this group of patients with DPOS.

RESULTS

Twelve patients were male, and 17 patients were female. The patients ranged in age from 15 years to 65 yrs (average, 36 years; median, 32 years). One tumor involved the scapula, one involved the ilium, and another involved the skull. All 26 of the other tumors were located in the long bones (14 in the femur, 5 in the humerus, 3 in the tibia, 3 in the fibula, and 1 in the ulna). In 18 patients, radiographic areas of lucency were seen within an otherwise sclerotic lesion. Histologically, the dedifferentiated component was high-grade osteoblastic osteosarcoma in 14 patients, fibroblastic osteosarcoma in 10 patients, giant cell-rich osteosarcoma in 3 patients, and chondroblastic osteosarcoma in 2 patients. All tumors were Stage IIB, and invasion of the medullary canal was detected in 19 patients (65%). Twenty-eight patients underwent surgery, and 18 of those patients received chemotherapy (5 patients received neoadjuvant chemotherapy, and 13 patients received adjuvant). Nine patients were dead and 20 patients were alive (average follow-up, 107 months; range, from 3 months to 36 years) at the last follow-up. Of the nine patients who died, one patient received no treatment, five patients underwent surgery (with three patients achieving adequate margins) in combination with chemotherapy, and three patients underwent surgery only (with adequate margins achieved). Of the 20 patients who remained alive, 13 patients underwent surgery (with 10 patients achieving adequate margins) in combination with chemotherapy, whereas 7 patients underwent surgery only (all with adequate margins). Seven of the nine patients who died had widespread metastases. One patient died of causes unrelated to the tumor, and another patient died shortly after undergoing resection of a lesion in the skull.

CONCLUSIONS

Dedifferentiation occurred in approximately 24% of patients with c-POS. The prognosis for patients with DPOS was better than the prognosis for patients with dedifferentiated central and dedifferentiated peripheral chondrosarcoma.

Myxoinflammatory fibroblastic sarcoma with complex supernumerary ring chromosomes composed of chromosome 3 segments

Myxoinflammatory fibroblastic sarcoma is a rare, recently described, and distinctive low-grade tumor of soft tissue. To our knowledge, there is only one previous report on the cytogenetics of this tumor. That case showed complex structural abnormalities, including a reciprocal translocation between chromosomes 1 and 10 [t(1;10)(p22;q24)] with loss of chromosomes 3 and 13. We describe here a second case showing supernumerary ring chromosomes, and a derivative chromosome 13, with additional material on the short arm. We conclude that the presence of chromosomal abnormalities supports the neoplastic nature of this tumor and aids in its diagnosis. Furthermore, we also postulate that the finding of ring chromosomes, which have been identified in other low-grade soft-tissue tumors, may have important prognostic implications regarding the aggressiveness of this neoplasm.

Characterization of large chromosome markers in a malignant fibrous histiocytoma by spectral karyotyping, comparative genomic hybridization (CGH), and array CGH

In this study, we characterized the chromosomal composition of an intra-abdominal soft tissue sarcoma diagnosed as a malignant fibrous histiocytoma (MFH). By applying a combination of spectral karyotyping, G-banding, and comparative genomic hybridization (CGH), this case was shown to carry large chromosome markers with material mainly from chromosomes 6 and 8. Further characterization of this unique tumor revealed high-level amplifications at the 6q21 approximately q23, 8p21 approximately pter, 8q24 approximately qter, and 12q13 approximately q21 regions. Using array CGH, these amplified regions were found to include MASL1 in 8p, as well s MDM2 and CDK4 in 12q, which have been shown to be amplified in MFH. Similarly, gains of 6q and 8q have also been seen in MFH. In conclusion, our study demonstrates the occurrence of large chromosome markers in MFH and suggests that the regions 6q21 approximately q23, 8p21 approximately pter, 8q24 approximately qter, and 12q13 approximately q21 might harbor oncogenes that could play a role in MFH's tumorigenesis. In addition, gain of 12q13 approximately q21, which is typical of well-differentiated liposarcoma, may also occur in MFH, supporting the previously suggested overlap in genetic etiologies between these two tumor types.

Genetics of dermatofibrosarcoma protuberans family of tumors: from ring chromosomes to tyrosine kinase inhibitor treatment

Dermatofibrosarcoma protuberans (DP) is a rare, slow-growing, infiltrating dermal neoplasm of intermediate malignancy, made up of spindle-shaped tumor cells often positive for CD34. The preferred treatment is wide surgical excision with pathologically negative margins. At the cytogenetic level, DP cells are characterized by either supernumerary ring chromosomes, which have been shown by using fluorescence in situ hybridization techniques to be derived from chromosome 22 and to contain low-level amplified sequences from 17q22-qter and 22q10-q13.1, or t(17;22), that are most often unbalanced. Both the rings and linear der(22) contain a specific fusion of COL1A1 with PDGFB. Similar to other tumors, the COL1A1-PDGFB fusion is occasionally cryptic, associated with complex chromosomal rearrangements. Although rings have been mainly observed in adults, translocations have been reported in all pediatric cases. DP is therefore a unique example of a tumor in which (i) the same molecular event occurs either on rings or linear translocation derivatives, (ii) the chromosomal abnormalities display an age-related pattern, and (iii) the presence of the specific fusion gene is associated with the gain of chromosomal segments, probably taking advantage of gene dosage effects. In all DP cases that underwent molecular investigations, the breakpoint localization in PDGFB was found to be remarkably constant, placing exon 2 under the control of the COL1A1 promoter. In contrast, the COL1A1 breakpoint was found to be variably located within the exons of the alpha-helical coding region (exons 6-49). No preferential COL1A1 breakpoint and no correlation between the breakpoint location and the age of the patient or any clinical or histological particularity have been described. The COL1A1-PDGFB fusion is detectable by multiplex RT-PCR with a combination of forward primers designed from a variety of COL1A1 exons and one reverse primer from PDGFB exon 2. Recent studies have determined the molecular identity of "classical" DP, giant cell fibroblastoma, Bednar tumor, adult superficial fibrosarcoma, and the granular cell variant of DP. In approximately 8% of DP cases, the COL1A1-PDGFB fusion is not found, suggesting that genes other than COL1A1 or PDGFB might be involved in a subset of cases. It has been proposed that PDGFB acts as a mitogen in DP cells by autocrine stimulation of the PDGF receptor. It is encouraging that inhibitory effects of the PDGF receptor tyrosine kinase antagonist imatinib mesylate have been demonstrated in vivo; such targeted therapies might be warranted in the near future for treatment of the few DP cases not manageable by surgery.

Differentially amplified chromosome 12 sequences in low- and high-grade osteosarcoma

Most osteosarcomas are highly aggressive malignancies characterized by a complex pattern of chromosome abnormalities. However, a subgroup of low-grade, parosteal tumors exhibits a relatively simple aberration pattern dominated by ring chromosomes carrying amplified material from chromosome 12. To assess whether sequences from this chromosome were differentially amplified in low- and high-grade osteosarcomas, copy numbers of the CCND2, ETV6, KRAS2, and D12S85 regions in 12p and the MDM2 region in 12q were evaluated by interphase or metaphase fluorescence in situ hybridization (FISH) in 24 osteosarcomas. Amplification of MDM2 was detected in all five low-grade and four high-grade osteosarcomas, all of which showed ring chromosomes. An overrepresentation of 12p sequences was found in 1/5 low-grade and in 9/19 high-grade tumors. Multicolor single-copy FISH analysis of metaphase cells from six high-grade tumors showed that extra 12p material either occurred together with MDM2 in ring chromosomes or was scattered over the genome as a result of complex structural rearrangements. Most tumors (8/10) not containing amplification of the assessed chromosome 12 loci exhibited a nondiploid pattern at evaluation with probes for centromeric alpha satellite sequences. These findings indicate that gain of sequences from the short arm of chromosome 12 could be a possible genetic pathway in the development of aggressive osteosarcoma.

Overrepresentation of 17q22-qter and 22q13 in dermatofibrosarcoma protuberans but not in dermatofibroma: a comparative genomic hybridization study

Histopathological differentiation between dermatofibrosarcoma protuberans (DFSP) and dermatofibroma (DF) is often difficult, because both neoplasms share some clinical features and the presence of a storiform pattern. In the present study, we investigated the usefulness of comparative genomic hybridization (CGH) in the diagnosis of these entities by examining 12 DFSP and 12 DF cases. The most frequent DNA sequence copy number changes detected in 10 (83%) of 12 DFSP cases (mean, 1.9 aberrations/tumor; range, 0-3) consisted of gains of 17q22-qter (10 tumors), 22q13 (nine tumors), and 8q24.1-qter (three tumors). High-level amplification, which was detected in three tumors, was seen only in chromosome 17, with 17q23-q25 as the minimal common region. Loss of DNA sequences was not found in DFSP cases. In contrast, two (17%) of the 12 DF cases (mean, 0.5 aberrations/tumor; range, 0-4) showed DNA sequence copy number changes, although recurrent gains and losses and high-level amplifications were not observed. Gains were more common than losses in DF. Overrepresentation of 17q and 22q sequences was a common finding in DFSP but not in DF. Thus, CGH seems to be useful for distinguishing DFSP from DF in most cases.

Transdifferentiation of neoplastic cells

Transdifferentiation is a process in which a stable cell's phenotype changes to that of a distinctly different cell type. It occurs during certain physiological processes and leads to transition of tumor cell phenotypes. The latter process includes neoplastic epithelial-epithelial transition, neoplastic epithelial-mesenchymal transition, neoplastic mesenchymal-epithelial transition and transition between non-neural and neural neoplastic cell. This phonomenon is exemplified in some origin-debated tumors, such as carcinosarcoma, pleomorphic adenoma, synovial sarcoma, Ewing's/pPNET, and malignant fibrohistiocytoma. We propose that differentiation disturbance of cancer cells should include not only undifferentiation and dedifferentiation, but also transdifferentiation as well. Tumor cell transdifferentiation may be influenced or determined by cellular genetic instabilities, proliferation and apoptosis, as well as by extracellular matrix and growth factors.

Supernumerary ring chromosomes in dermatofibrosarcoma protuberans may contain sequences from 8q11.2-qter and 17q21-qter: a combined cytogenetic and comparative genomic hybridization study

Dermatofibrosarcoma protuberans (DFSP) presents with characteristic cytogenetic features such as reciprocal t(17;22)(q22;q13) or, more commonly, supernumerary ring chromosomes containing sequences from chromosomes 17 and 22. Here, we report the identification of a novel abnormality in a 43-year-old woman with DFSP. Cytogenetic analysis of tumor cells showed the presence of a supernumerary ring chromosome as the sole anomaly. Amplification of 8q11.2 approximately qter and 17q21 approximately qter sequences was confirmed by comparative genomic hybridization (CGH); the present case apparently lacked amplification of chromosome 22. To our knowledge, this is the first case indicating that the ring chromosome in DFSP is possibly associated with amplified material from chromosomes 8 and 17.

Spectral karyotyping reveals 17;22 fusions in a cytogenetically atypical dermatofibrosarcoma protuberans with a large marker chromosome as a sole abnormality

The presence of an extra ring chromosome containing material from 17q and 22q, or, less frequently, a t(17;22)(q22;q13), is a cytogenetic hallmark of dermatofibrosarcoma protuberans (DFSP). However, occasionally tumors with other, atypical karyotypes are encountered. We describe a case of recurrent DFSP without a ring chromosome or a t(17;22) on standard cytogenetic analysis. In all cells analyzed by G-banding, an additional, large marker chromosome was present as a sole abnormality. This chromosome apparently included chromosome 8 or the 8q arm, but the origin of its remaining part could not be determined with certainty. To characterize further the abnormal chromosome, we applied spectral karyotyping (SKY). SKY confirmed the presence of an extra chromosome 8 or arm 8q in the marker and showed that its remaining part was composed of segments from chromosomes 7, 17, 21, and 22, with two copies of a 17;22 fusion. Our results and the literature data suggest that, in addition to a specific 17;22 fusion, amplification of material from chromosomes 17, 22, 8, 5, 7, and 21 may play a role in DFSP development and/or progression. Furthermore, our case demonstrates the usefulness of SKY in detection of a diagnostically relevant 17;22 fusion in DFSP patients who have unusual karyotypic features.

Translocation (2;15)(p23;q21.2) and interstitial deletion of 7q in a case of low-grade myxofibrosarcoma

We describe a case of low-grade myxofibrosarcoma with the karyotype 46,XX,t(2;15)(p23;q21.2), del(7)(q?11.2q?22). Only six of these tumors have been previously studied and all were cytogenetically different.

Novel cell lines established from a human myxoid malignant fibrous histiocytoma arising in the uterus

Two cell lines (Nara-H and Nara-F) with different phenotypes were established from a myxoid MFH of the uterus. In vitro, Nara-F grew in sheets showing a storiform arrangement and Nara-H in raised colonies. Although tumors generated in nude mice shared similar morphological features of abundant myxoid tumor in Nara-H and -F, the pleomorphic component was conspicuous in Nara-F. Both cell lines produced hyaluronic-acid but CD44 was expressed only in Nara-H. Estrogen receptor alpha (ER alpha) and progesterone receptor (PgR) were detected in Nara-H. Nara-F was positive for ER beta and PgR. Among hormonal agents, the response to the anti-estrogen tamoxifen was more sensitive than progesterone agents. This report illustrates the characteristics of these newly established cell lines, and presents the possibility of an adjuvant hormonal therapy for MFH.

Low grade fibromyxoid sarcoma. a further low-grade soft tissue malignancy characterized by a ring chromosome

Supernumerary rings in the context of a simple karyotype characterize several low-grade malignant tumors of soft tissue and bone. Low-grade fibromyxoid sarcoma is an uncommon low-grade sarcoma, the cytogenetics of which has not yet been reported. Here we describe the first molecular-cytogenetic characterization of a pulmonary metastasis of low-grade fibromyxoid sarcoma. The histology of the primary and recurrent tumors was consistent with the diagnosis of low-grade fibromyxoid sarcoma of the usual type, whereas the pulmonary metastasis was of the "giant rosettes" variant. Cytogenetic analysis revealed a ring chromosome. Because gain of material of chromosomes 7 and 16 was detected by CGH, the ring chromosome is assumed to be composed of material from these respective chromosomes.

Cytogenetic evidence of clonality in cutaneous benign fibrous histiocytomas: a report of the CHAMP study group

AIMS

Cutaneous benign fibrohistiocytic tumours are among the most common soft tissue lesions. Their biological nature, in particular whether they are neoplastic or reactive, has long been disputed. Some morphological subtypes can be confused with sarcoma. Since available karyotypic data in these lesions are scarce, this study was undertaken to determine whether their cytogenetic analysis might demonstrate clonality and might help in differential diagnosis.

METHODS AND RESULTS

Thirteen karyotyped benign cutaneous fibrous histiocytomas (BFH) were morphologically reassessed and classified as ordinary BFH (eight cases), cellular BFH (four cases), and one ankle-type lesion. Five cases (38%) showed clonal cytogenetic changes, although the aberrations varied and did not correlate with histological subtypes. Karyotypic aberrations were more common in cellular BFH (3/4) than in the ordinary BFH (2/8).

CONCLUSIONS

The demonstration of clonal chromosome abnormalities, in at least some cases, supports the neoplastic nature of cutaneous BFH. The karyotypic changes identified are different from those in dermatofibrosarcoma, with which cellular BFH is often confused histologically.

Chromosomal breakage-fusion-bridge events cause genetic intratumor heterogeneity

It has long been known that rearrangements of chromosomes through breakage-fusion-bridge (BFB) cycles may cause variability of phenotypic and genetic traits within a cell population. Because intercellular heterogeneity is often found in neoplastic tissues, we investigated the occurrence of BFB events in human solid tumors. Evidence of frequent BFB events was found in malignancies that showed unspecific chromosome aberrations, including ring chromosomes, dicentric chromosomes, and telomeric associations, as well as extensive intratumor heterogeneity in the pattern of structural changes but not in tumors with tumor-specific aberrations and low variability. Fluorescence in situ hybridization analysis demonstrated that chromosomes participating in anaphase bridge formation were involved in a significantly higher number of structural aberrations than other chromosomes. Tumors with BFB events showed a decreased elimination rate of unstable chromosome aberrations after irradiation compared with normal cells and other tumor cells. This result suggests that a combination of mitotically unstable chromosomes and an elevated tolerance to chromosomal damage leads to constant genomic reorganization in many malignancies, thereby providing a flexible genetic system for clonal evolution and progression.

Myxoid tumours of soft tissue

Myxoid tumours of soft tissue encompass a heterogeneous group of lesions characterized by a marked abundance of extracellular mucoid (myxoid) matrix. This group of tumours demonstrate significant variability in their biological behaviour thus including tumours which are entirely harmless, tumours with a tendency to recur locally but not metastasize, and malignant tumours. There appears to be a considerable degree of overlap clinically and morphologically between the various tumour types in this group, generating potential diagnostic problems for the clinician and pathologist alike. While diligent microscopy remains the basis of diagnostic pathology, the continuous developments and refinements within the fields of immunohistochemistry and molecular cytogenetics are providing substantial new information, allowing the development of new diagnostic criteria and hence facilitating an accurate diagnosis. It is the aim of this short review to highlight the most prevalent soft tissue tumours with predominantly myxoid morphology, to describe the features by which the majority of these myxoid lesions may be identified, and to discuss the differential diagnosis where appropriate.

A progression to dermatofibrosarcoma protuberans with a fibrosarcomatous component: a special reference to the chromosomal aberrations

Dermatofibrosarcoma protuberans (DFSP) with fibrosarcomatous areas (DFSP-FS) is differentiated from ordinary DFSP by its unfavourable prognosis. We carried out sequential analysis of numerical chromosomal abnormalities in two cases of DFSP during their progression to metastatic disease with FS areas (DFSP-M-FS). They were compared with nine cases of ordinary DFSP and three cases of DFSP-FS, but without metastases. Numerical chromosomal changes were examined by fluorescence in situ hybridization (FISH) using alpha-satellite centromeric probes for chromosomes 1, 8, 11 and 17. Numerical imbalances of chromosome 1 were not clarified. A gain of chromosome 8 was demonstrated in the two cases of DFSP-M-FS. A gain of chromosome 11 was observed in one of the two cases of DFSP-M-FS and in one case of DFSP-FS. A gain of chromosome 17 was demonstrated in both metastatic tumours and in recurrent tumours in two cases of DFSP-M-FS, in addition to two cases of DFSP-FS and four cases of ordinary DFSP with recurrent tumours or large tumours. This study raised the hypothesis that a gain of chromosome 17 developed in recurrent or large-sized DFSP, which occurs in high-risk groups with the possibility of a progression to FS.

Identification of a ring chromosome in a myxoid malignant fibrous histiocytoma with chromosome microdissection and fluorescence in situ hybridization

We investigated the origin of a ring chromosome in a myxoid malignant fibrous histiocytoma (MFH) by microdissection and fluorescence in situ hybridization (FISH) analyses. Cytogenetically, only two ring chromosomes were observed; the smaller ring was seen more frequently. The latter was microdissected, and the material used for FISH. Hybridization of the microdissected labeled DNA to normal metaphase cells revealed that the signal localized only to 20q. Three signals were seen in the tumor cells using either the microdissected 20q probe or chromosome 20 centromeric probe, indicating the involvement of both the long arm and the centromere in the ring chromosome. The short arm of chromosome 20 did not appear to be involved in the formation of the ring chromosome.

Co-amplification and overexpression of CDK4, SAS and MDM2 occurs frequently in human parosteal osteosarcomas

Amplification of genes in the 12q13-15 region occurs frequently in several malignancies including osteosarcoma. The products of these amplified genes are thought to provide cancer cells with a selective growth advantage; however, the specific gene(s) driving this amplicon is unknown. We have previously shown that the SAS gene is amplified in most parosteal osteosarcomas. In this study we analysed additional putative growth regulatory genes in this chromosomal region in 24 primary osteosarcoma specimens. CDK4 and SAS were coamplified in 6/6 parosteal tumors, and MDM2 was also amplified in 4/5 parosteal cases. In comparison, amplification occurred in only 2/16 classical intramedullary osteosarcomas and involved the SAS gene. Each amplified gene had a correspondingly elevated mRNA level. Four high grade intramedullary tumors had elevated mRNA expression of SAS, but did not exhibit gene amplification. Gene amplification/overexpression was not associated with metastatic disease and did not change markedly with tumor progression, as evidenced by analysis of sequential tumor specimens from eight patients. Three other genes in the 12q13-15 region (CDK2, WNT1 and WNT10b) were not amplified in any of the tumors. The different patterns of gene amplification and overexpression of CDK4, SAS and MDM2 in parosteal and intramedullary osteosarcomas may help explain the disparity in the biological behaviour of these two types of osteosarcoma.

Amplification of 12q13 and 12q15 sequences in a sclerosing epithelioid fibrosarcoma

Sclerosing epithelioid fibrosarcoma (SEF) is a recently described entity. It is a low-grade sarcoma that occurs primarily in the deep soft tissues of the extremities of adults. It may histologically simulate benign lesions such as fibroma and myxoma or malignancies such as sclerosing carcinoma and lymphoma, extraskeletal myxoid chondrosarcoma, clear cell sarcoma of tendons and aponeuroses, and synovial sarcoma, depending on the lesion's cellularity, degree of fibrosis, and amount of myxoid matrix. There are no previously published cytogenetic studies of this tumor. We found the karyotype 40-45,XY,add(9)(p13),add(10)(p11),-12,-13,-18,add(18)(q11),add(20)(q11) in a SEF of a 14-year-old boy, by using chromosome banding. Fluorescence in situ hybridization showed that both the add(10) and the add(18) contained amplified sequences from 12q13 and 12q15, including the HMGIC gene. Chromosome 18 material was present in the add(9) and terminally in the add(10). The karyotype of this case indicates that SEF is unrelated to extraskeletal myxoid chondrosarcoma, clear cell sarcoma, and synovial sarcoma. When compared with the findings in other soft tissue tumors such as well-differentiated liposarcoma and low-grade malignant fibrous histiocytoma, the chromosome banding and in situ hybridization data add support to the notion that SEF is a relatively low grade variant of fibrosarcoma.

A case of dermatofibrosarcoma protuberans with a ring chromosome 5 and a rearranged chromosome 22 containing amplified COL1A1 and PDGFB sequences

Dermatofibrosarcoma protuberans (DFSP) is a cutaneous tumour of borderline malignancy, the cytogenetic features of which include the translocation t(17;22)(q22;q13) or, more commonly, supernumerary ring chromosomes containing material from 17q22 and 22q13. These rearrangements result in the COL1A1/PDGFB fusion gene. Here, we describe a case of DFSP displaying a ring chromosome 5 together with a large marker chromosome composed of chromosome 22 alphoid DNA, material from distal 12q and amplified COL1A1 and PDGFB sequences. This is the first case of DFSP with multiple copies of COL1A1 and PDGFB not confined to ring chromosomes, showing that DFSP is similar to other borderline malignant mesenchymal tumours, where rings and giant markers are alternative vehicles for amplified material.

Chromosomal organization of amplified chromosome 12 sequences in mesenchymal tumors detected by fluorescence in situ hybridization

The chromosomal organization of amplified chromosome 12 sequences was studied with fluorescence in situ hybridization in six mesenchymal tumors: two osteosarcomas, one lipoma, two liposarcomas, and one fibrosarcoma. All except the fibrosarcoma contained ring and/or giant marker chromosomes. Amplification of chromosome 12 sequences, demonstrated with whole-chromosome paint in all cases, was confined to ring and giant marker chromosomes in four tumors. In one of the osteosarcomas and in the fibrosarcoma, amplified sequences were added to chromosome 12 and to chromosomes 10, 12, 18, and the Y chromosome, respectively. Hybridizations with single-copy probes demonstrated considerable inter- and intracellular variation in the arrangement of chromosome 12 sequences in ring and marker chromosomes. Amplification of 12q13-15 sequences, predominantly from the HMGIC-MDM2 region, was detected in all cases, but the two osteosarcomas also contained amplification of 12p material. This finding, combined with results from previous studies, indicates that 12p amplification is a feature distinguishing osteosarcomas from adipose tissue tumors. A novel finding was the presence of positive signals for chromosome 12 alpha-satellite sequences in ring and marker chromosomes in four cases. Rod chromosomes carrying amplified material, in particular those that were relatively stable, frequently exhibited chromosome 12 negative terminal segments; two of these, present in two separate cases, were shown by C-banding to contain constitutive heterochromatin. The significant intercellular heterogeneity in the number and structure of rings and giant markers in a subset of mesenchymal tumors could be explained by continuous recombination through breakage-fusion-bridge cycles. If so, this process will continue until broken ends become stabilized, for example by acquisition of telomeric segments from other chromosomes.

Molecular characterization of a novel amplicon at 1q21-q22 frequently observed in human sarcomas

In a recent comparative genomic hybridization (CGH) study of a panel of sarcomas, we detected recurrent amplification of 1q21-q22 in soft tissue and bone tumours. Amplification of this region had not previously been associated with sarcoma development, but occasional amplification of CACY/S100A6 and MUC1 in 1q21 had been reported for melanoma and breast carcinoma respectively. Initial screening by Southern blot analysis showed amplification of S100A6, FLG and SPRR3 in several sarcomas and, in a first attempt to characterize the 1q21-q22 amplicon in more detail, we have now investigated the amplification status of these and 11 other markers in the region in 35 sarcoma samples. FLG was the most frequently amplified gene, and the markers located in the same 4.5-Mb region as FLG showed a higher incidence of amplification than the more distal ones. However, for most of the 14 markers, amplification levels were low, and only APOA2 and the anonymous marker D1S3620 showed high-level amplifications (> tenfold increases) in one sample each. We used fluorescence in situ hybridization (FISH) to determine the amplification patterns of two overlapping yeast artificial chromosomes (YACs) covering the region between D1S3620 and FLG (789f2 and 764a1), as well as two more distally located YACs in nine selected samples. Six samples had amplification of the YAC containing D1S3620 and, in three, 764a1 was also included. Five of these tumours showed normal copies of the more distal YACs; thus, it seems likely that an important gene may be located within 789f2, or very close. Two samples had high copy numbers of the most distal YACs. Taken together, FISH and molecular analyses indicate complex amplification patterns in 1q21-q22 with at least two amplicons: one located near D1S3620/789f2 and one more distal.

Characterization of a human myxoid malignant fibrous histiocytoma cell line, OH931

Malignant fibrous histiocytoma (MFH), the most common soft-tissue sarcoma of late adult life, includes several histopathologic subtypes. The myxoid MFH subtype is characterized by the presence of abundant mucopolysaccharide within a loose connective tissue stroma. Although the myxoid variant is typically distinguished clinically by its better prognosis, we report a case of myxoid MFH that exhibited an aggressive phenotype with early metastases and death. A cell line, OH931, was established from this myxoid MFH. The primary tumor, OH931 cell line, and cells recovered from tumors generated in nude mice shared similar morphologic features, including the continued production of abundant mucopolysaccharide. Cytogenetic analysis of the primary tumor and a subsequently established cell line (OH931) revealed a complex hypertriploid mainline. Chromosomal breakpoints involved in all three specimens analyzed (diagnostic biopsy, definitive surgical, and cell line) included 1p33, 1q21, 2p14, 4p15, 5q13, 12q13, 14p13, 15p13, 19q13 and 20q13.1. The OH931 cell line, which appears to maintain its peculiar characteristics in vitro, should be useful in studies investigating the role of mucopolysaccharide production in the process of neoplasia.

Cytogenetic studies in malignant fibrous histiocytoma

Among soft tissue sarcomas, malignant fibrous histiocytoma is considered to be the most commonly encountered tumor-type of late adult life. Cytogenetic data are, however, sparse and contradictory, without any specific anomalies. We are describing the results of cytogenetic studies in 20 malignant fibrous histiocytomas of various subtypes and gradings. Although we saw two single and therefore possibly primary rearrangements, t(13;14) and t(5;7), most tumors had complex rearrangements without sharing any characteristic aberrations. In our opinion, the heterogeneity of these findings supports the concept that malignant fibrous histiocytoma is not a distinctive entity but merely a name for a group of as yet poorly defined sarcomas.

Molecular and cytogenetics of soft tissue sarcomas

Molecular and cytogenetically soft tissue sarcomas are a well-characterized tumor entity with several tumor type specific changes understood also at the molecular level. Most likely, additional characteristic alterations will be detected, recurrent aberrations characterized at the molecular level, new clinical and histopathological correlations will be found, and little is known about how the genetic changes lead to tumor formation, promote progression and sometimes give tumor cells the ability to recur locally or distantly. The possibility to detect cells with these acquired genetic alterations may increase the reproducibility of tumor classification, yields promising possibilities for early diagnosis of tumor recurrences and/or metastasis, and may allow development of therapeutic regimens targeted at the genetically alterated cell.

Musculoskeletal oncology--advances in cytogenetics and molecular genetics and their clinical implications

Although musculoskeletal malignancies comprise a small group of cancers, a vast number of histological subtypes have been identified attesting to the heterogeneity of this class of tumours and the growing interest in their development. The mode of management for both bone and soft tissue sarcomas has been examined extensively and treatment guidelines have been proposed. Despite the intensive study and multidisciplinary treatment, a substantial proportion of tumours remain recalcitrant to therapy and recur locally and systemically. Improved methods of characterising these tumours may help in understanding their biology. Cytogenetic and molecular genetic techniques allow a subcellular dissection of these malignancies which may aid the identification of mechanisms that are important in tumorigenesis. Already candidate genes have been isolated which may play an important role in the deregulation of proliferation and or the adoption of a malignant phenotype, features which are fundamental in tumour development. By studying the molecular biology and cytogenetics of tumours it may be possible to improve diagnostic and prognostic accuracy thereby minimising over and under treatment.

Karyotypic characteristics of borderline malignant tumors of the ovary: trisomy 12, trisomy 7, and r(1) as nonrandom features

Clonal karyotypic abnormalities were detected in five of 14 cytogenetically analyzed borderline malignant ovarian tumors of clinical stages I-II. One mucinous and one seropapillary tumor had trisomy 7 and r(1)(p36q42) as the sole chromosome abnormality, respectively. Trisomy 12 was found in the remaining three cases. It was the only change in one mucinous and one serous tumor, whereas the third, a seropapillary borderline tumor, had the karyotype 49,XX,+5,+8, +12. These findings, especially when collated with those of previous reports on ovarian borderline tumor cytogenetics, indicate that +12 is the most consistent chromosomal aberration in this group of neoplasms and that also +7 and r(1) are nonrandom features. From the karyotypic point of view, benign ovarian tumors and well-differentiated carcinomas are similar to borderline ovarian tumors, with the possible exception that the former have no tendency to form r(1). Highly malignant carcinomas, on the other hand, are typically much more complex. Chromosome-level changes therefore cannot account for the putative phenotypic passage through the most innocuous tumor stages as epithelial ovarian neoplasms go from benign to fully malignant.

Presence of double minutes and monosomy 17p in xenografted human osteosarcomas

Cytogenetic analysis of 8 cases of xenografted human osteosarcomas are reported, including six newly diagnosed and two recurrent tumors. Histologically five were osteoblastic, two were chondroblastic, and one was the microcellular type. All tumors were studied in short-term primary cultures between two and six days. Clonal and nonclonal abnormalities were present in the eight cases; four had a chromosome number in the hypotriploid range, two in the hyperdiploid, one in the hypodiploid, and one in the hypertetraploid range. All cases had complex karyotypes and the recognizable structural rearrangements clustered to chromosome arms 1p, 1q, 3p, 5p, 6q, 11p, 13p, 14p, 15q, 16p, 16q, 20q, 21p, and 22q. Seven cases presented double monosomy 17 and six tumors showed double minutes (dmin) or a homogeneously staining region (hsr). This fact has been described recently and its relation with the amplification of the MDM2 gene observed in osteosarcomas is as yet unknown.

Loss of an X chromosome in aggressive angiomyxoma of female soft parts: a case report

Cytogenetic analysis of an aggressive angiomyxoma of the vulvar region of a 16-year-old female revealed loss of one X chromosome (45,X,-X) in eight of 20 metaphase cells analyzed. Fluorescence in situ hybridization (FISH) performed on disaggregated cells from paraffin embedded lesional tissue confirmed loss of an X chromosome in 31% of cells. Cytogenetic analysis performed on peripheral blood showed a normal chromosomal complement (46,XX). Thus, loss of one X chromosome appears to be confined to the neoplasm. This anomaly has not been previously described in aggressive angiomyxoma.

19p+ marker chromosome correlates with relapse in malignant fibrous histiocytoma

In this study, we examined the relationship of 19p13 aberrations, usually leading to addition of unknown material (19p+), and ring chromosomes to clinical outcome in patients with malignant fibrous histiocytoma (MFH). Analysis of 69 MFHs revealed 19 tumors with 19p+ and 24 tumors with ring chromosomes. After a median follow-up period of 36 months, 24 patients developed metastases, and 27 patients developed local recurrences. Ten patients had both local recurrences and metastases. Local recurrence was more common in association with 19p+ than without. Metastasis was more common with 19p+ tumors in high-risk patients (tumor size > 5 cm and grade III-IV; n = 48) than those without 19p+. There was a trend suggesting fewer relapses after tumors with ring chromosomes. 19p+ may be an independent marker of unfavorable outcome in MFH.

Ring chromosomes in parosteal osteosarcoma contain sequences from 12q13-15: a combined cytogenetic and comparative genomic hybridization study

Seven parosteal osteosarcoma (POS) samples, six of which were cytogenetically characterized, were studied by using comparative genomic hybridization (CGH). All samples showed DNA sequence copy number changes (mean, six aberrations/tumor; range, 1-13); gains were more frequent than losses. Gain of 12q13-15 sequences was found in every tumor and correlated with the presence of ring chromosomes. High-level amplification, which was detected in four tumors, was seen only in chromosome 12, with 12q13-14 as the minimal common region. By using chromosome painting, one of the rings of one case was shown to be composed entirely of chromosome 12 material. Together with previous data, our findings show that gain of 12q13-15 sequences is a characteristic feature of POS and that these sequences are contained within the ring chromosomes.

A cytogenetic study of malignant fibrous histiocytoma

We report the results of cytogenetic analysis of malignant fibrous histiocytoma of soft tissue (MFH). Seven of 12 successfully cultured MFHs had complex clonal aberrations, including translocations, deletions, and unidentifiable marker chromosomes. Telomeric associations were observed in five and the double minute phenomenon in four of seven MFHs with abnormal karyotypes. In one case (a storiform-pleomorphic MFH, grade IV) with a complex polyploid karyotype, two clonal ring chromosomes were present, one interpreted as r(19)(p13q13), one unidentified. In two tumors, clonal structural rearrangements of chromosome 1 were seen: del(1)(q21) in a storiform-pleomorphic MFH, grade IV, and add (1)(q21 or q32), t(1;10)(p22;q22) in a myxoid MFH, grade I. The remaining five MFHs had normal karyotypes, but in two of them nonclonal, structural aberrations were found. The modal chromosome number in the studied MFHs varied widely, but the majority of tumors with abnormal karyotypes had polyploid chromosome complements (five of seven cases). Our results confirm many of the previous findings and indicate that double minutes (dmins) may be more frequent in MFH than previously reported.

Characterization of the 12q13-15 amplicon in soft tissue tumors

Amplification of the genes MDM2, SAS, and CDK4, all located on the long arm of chromosome 12, has recently been demonstrated in human soft tissue tumors. To determine the extent of the amplification unit, we examined 16 soft tissue tumor samples, including pleomorphic liposarcoma, malignant fibrous histiocytoma (MFH), and atypical lipoma, by Southern blot analysis using 13 chromosome 12 probes. All tumors had previously been shown to have 3- to 20-fold amplification of MDM2. In five samples, all MFH, only MDM2 was amplified, whereas in the remaining 11 samples, two to five additional genes were amplified. The amplicon included markers both proximal and distal to MDM2, but was in all but one atypical lipoma confined to the chromosome region 12q13-15. Discontinuous amplicons were found in two of the tumors. This study indicates that MDM2, or possibly an as-yet-unidentified gene in its proximity, is the target gene of the 12q13-15 amplification in soft tissue tumors.