Molecular characteristics of lung adenocarcinoma with respect to patient age at diagnosis.

Lung cancer is primarily a disease of the elderly, with a median age at diagnosis around 70 years. In our study we sought to address the question of whether and how clinical characteristics, molecular alterations and molecular phenotypes differ between patient populations with early-stage lung adenocarcinoma (AC) with respect to age at diagnosis. Patients were stratified based on age at diagnosis into five systematic age bins (<50, 50-60, 60-70, 70-80 and ≥80 years). To assess clinicopathological variables on a population-based level, we accessed data from the national quality registry for lung cancer in Sweden. In parallel, we used compiled datasets from public cohorts to investigate focal and genome-wide DNA alterations, epigenetic alterations, immune composition and transcriptional patterns in relation to age at diagnosis. Gender, stage, WHO performance and likelihood of receiving chemotherapy as adjuvant treatment were linked to age at diagnosis. Associations between younger patient age and likelihood of harboring certain driver mutations (eg, in EGFR and ALK) were confirmed. We also found an association between age at diagnosis and certain mutational signatures. However, age did not seem to drive transcriptional, copy number, or epigenetic variation in the tumors. Based on our findings, age at diagnosis alone does not appear to provide an additional layer of biological complexity above that of proposed genetic and transcriptional phenotypes of AC.

Proteogenomics of non-small cell lung cancer reveals molecular subtypes associated with specific therapeutic targets and immune evasion mechanisms.

Despite major advancements in lung cancer treatment, long-term survival is still rare, and a deeper understanding of molecular phenotypes would allow the identification of specific cancer dependencies and immune evasion mechanisms. Here we performed in-depth mass spectrometry (MS)-based proteogenomic analysis of 141 tumors representing all major histologies of non-small cell lung cancer (NSCLC). We identified six distinct proteome subtypes with striking differences in immune cell composition and subtype-specific expression of immune checkpoints. Unexpectedly, high neoantigen burden was linked to global hypomethylation and complex neoantigens mapped to genomic regions, such as endogenous retroviral elements and introns, in immune-cold subtypes. Further, we linked immune evasion with LAG3 via STK11 mutation-dependent HNF1A activation and FGL1 expression. Finally, we develop a data-independent acquisition MS-based NSCLC subtype classification method, validate it in an independent cohort of 208 NSCLC cases and demonstrate its clinical utility by analyzing an additional cohort of 84 late-stage NSCLC biopsy samples.

A gene expression-based single sample predictor of lung adenocarcinoma molecular subtype and prognosis.

Disease recurrence in surgically treated lung adenocarcinoma (AC) remains high. New approaches for risk stratification beyond tumor stage are needed. Gene expression-based AC subtypes such as the Cancer Genome Atlas Network (TCGA) terminal-respiratory unit (TRU), proximal-inflammatory (PI) and proximal-proliferative (PP) subtypes have been associated with prognosis, but show methodological limitations for robust clinical use. We aimed to derive a platform independent single sample predictor (SSP) for molecular subtype assignment and risk stratification that could function in a clinical setting. Two-class (TRU/nonTRU=SSP2) and three-class (TRU/PP/PI=SSP3) SSPs using the AIMS algorithm were trained in 1655 ACs (n = 9659 genes) from public repositories vs TCGA centroid subtypes. Validation and survival analysis were performed in 977 patients using overall survival (OS) and distant metastasis-free survival (DMFS) as endpoints. In the validation cohort, SSP2 and SSP3 showed accuracies of 0.85 and 0.81, respectively. SSPs captured relevant biology previously associated with the TCGA subtypes and were associated with prognosis. In survival analysis, OS and DMFS for cases discordantly classified between TCGA and SSP2 favored the SSP2 classification. In resected Stage I patients, SSP2 identified TRU-cases with better OS (hazard ratio [HR] = 0.30; 95% confidence interval [CI] = 0.18-0.49) and DMFS (TRU HR = 0.52; 95% CI = 0.33-0.83) independent of age, Stage IA/IB and gender. SSP2 was transformed into a NanoString nCounter assay and tested in 44 Stage I patients using RNA from formalin-fixed tissue, providing prognostic stratification (relapse-free interval, HR = 3.2; 95% CI = 1.2-8.8). In conclusion, gene expression-based SSPs can provide molecular subtype and independent prognostic information in early-stage lung ACs. SSPs may overcome critical limitations in the applicability of gene signatures in lung cancer.

Methylation Patterns and Chromatin Accessibility in Neuroendocrine Lung Cancer.

Lung cancer is the worldwide leading cause of death from cancer. Epigenetic modifications such as methylation and changes in chromatin accessibility are major gene regulatory mechanisms involved in tumorigenesis and cellular lineage commitment. We aimed to characterize these processes in the context of neuroendocrine (NE) lung cancer. Illumina 450K DNA methylation data were collected for 1407 lung cancers including 27 NE tumors. NE differentially methylated regions (NE-DMRs) were identified and correlated with gene expression data for 151 lung cancers and 31 human tissue entities from the Genotype-Tissue Expression (GTEx) consortium. Assay for transposase-accessible chromatin sequencing (ATAC-seq) and RNA sequencing (RNA-seq) were performed on eight lung cancer cell lines, including three NE cell lines, to identify neuroendocrine specific gene regulatory elements. We identified DMRs with methylation patterns associated with differential gene expression and an NE tumor phenotype. DMR-associated genes could further be split into six functional modules, including one highly specific gene module for NE lung cancer showing high expression in both normal and malignant brain tissue. The regulatory potential of NE-DMRs was further validated in vitro using paired ATAC- and RNA-seq and revealed both proximal and distal regulatory elements of canonical NE-marker genes such as CHGA, NCAM1, INSM1, as well as a number of novel candidate markers of NE lung cancer. Using multilevel genomic analyses of both tumor bulk tissue and lung cancer cell lines, we identified a large catalogue of gene regulatory elements related to the NE phenotype of lung cancer.

Recurrent Fusions Between YAP1 and KMT2A in Morphologically Distinct Neoplasms Within the Spectrum of Low-grade Fibromyxoid Sarcoma and Sclerosing Epithelioid Fibrosarcoma.

Sclerosing epithelioid fibrosarcoma (SEF) is an aggressive soft tissue sarcoma. In the majority of cases, there is overexpression of MUC4, and most cases show EWSR1-CREB3L1 gene fusions. A subset of SEF displays composite histologic features of SEF and low-grade fibromyxoid sarcoma (LGFMS). These "hybrid" tumors are more likely to harbor the FUS-CREB3L2 fusion, which is also seen in most LGFMS. We, here, characterize a series of 8 soft tissue neoplasms with morphologic features highly overlapping with LGFMS and SEF but lacking MUC4 expression and EWSR1/FUS-CREB3L gene fusions. Seven tumors showed fusions of the YAP1 and KMT2A genes, and 1 had a fusion of PRRX1 and KMT2D; all but 1 case displayed reciprocal gene fusions. At gene expression profiling, YAP1 and KMT2A/PRRX1 and KMT2D tumors were distinct from LGFMS/SEF. The patients were 4 female individuals and 4 male individuals aged 11 to 91 years. Tumors with known locations were in the lower extremity (5), trunk (2), and upper extremity (1); 3 originated in acral locations. Tumor size ranged from 2.5 to 13 cm. Proportions of SEF-like and LGFMS-like areas varied considerably among tumors. All tumors that showed infiltrative growth and mitotic figures per 10 HPFs ranged from 0 to 18. Tumor necrosis was present in 1 case. Follow-up was available for 5 patients (11 to 321 mo), 2 of whom developed local recurrences, and 1 died of metastatic disease. The clinical behavior of these soft tissue sarcomas remains to be further delineated in larger series with extended follow-up; however, our limited clinical data indicate that they are potentially aggressive.

Deep sequencing of myxoinflammatory fibroblastic sarcoma.

Myxoinflammatory fibroblastic sarcoma (MIFS) has recurrent genetic features in the form of a translocation t(1;10)(p22-31;q24-25), BRAF gene fusions, and/or an amplicon in 3p11-12 including the VGLL3 gene. The breakpoints on chromosomes 1 and 10 in the t(1;10) cluster in or near the TGFBR3 and OGA genes, respectively. We here used a combination of deep sequencing of the genome (WGS), captured sequences (Cap-seq), and transcriptome (RNA-seq) and genomic arrays to investigate the molecular outcome of the t(1;10) and the VGLL3 amplicon, as well as to assess the spectrum of other recurrent genomic features in MIFS. Apart from a ROBO1-BRAF chimera in a t(1;10)-negative MIFS-like tumor, no fusion gene was found at RNA-seq. This was in line with WGS and Cap-seq results, revealing variable breakpoints in chromosomes 1 and 10 and genomic breakpoints that should not yield functional fusion transcripts. The most common genomic rearrangements were breakpoints in or around the OGA, NPM3, and FGF8 genes in chromosome band 10q24, and loss of 1p11-p21 and 10q26-qter (all simultaneously present in 6/7 MIFS); a breakpoint in or near TGFBR3 in chromosome 1 was found in four of these tumors. Amplification and overexpression of VGLL3 was a consistent feature in MIFS and MIFS-like tumors with amplicons in 3p11-12. The significant molecular genetic outcome of the recurrent t(1;10) could be loss of genetic material from 1p and 10q. Other recurrent genomic imbalances in MIFS, such as homozygous loss of CDKN2A and 3p- and 13q-deletions, are shared with other sarcomas, suggesting overlapping pathogenetic pathways.

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.

Gene fusion involving the insulin-like growth factor 1 receptor in an ALK-negative inflammatory myofibroblastic tumour.

AIMS: Inflammatory myofibroblastic tumour (IMT) is a soft tissue tumour primarily affecting children and young adults. Approximately 50% of IMTs have gene fusions involving the receptor tyrosine kinase (RTK)-encoding ALK gene, providing a molecular rationale for treating IMT patients with unresectable tumours with tyrosine kinase inhibitors (TKI). However, a subset of IMT instead displays fusions affecting other RTKencoding genes, so far including NTRK3, PDGFRB and ROS1. Also, IMTs with variant RTK fusions may respond well to TKI treatment, but can be dif?cult to identify as they are negative for ALK staining at immunohistochemistry, the standard method for detection of ALK rearrangements. MATERIALS AND METHODS: We used RNA-sequencing to search for alternate fusion events in an ALK-negative IMT. RESULTS AND CONCLUSIONS: We found a novel fusion gene - FN1-IGF1R. The FN1 gene, encoding ?bronectin, is thought to provide a strong promoter activity for the kinase domain of the RTK insulin-like growth factor 1 receptor, a mechanism similar to previously described RTK fusions in IMT.

Aberrant receptor tyrosine kinase signaling in lipofibromatosis: a clinicopathological and molecular genetic study of 20 cases.

Lipofibromatosis is a rare pediatric soft tissue tumor with predilection for the hands and feet. Previously considered to represent "infantile fibromatosis", lipofibromatosis has distinctive morphological features, with mature adipose tissue, short fascicles of bland fibroblastic cells, and lipoblast-like cells. Very little is known about the genetic underpinnings of lipofibromatosis. Prompted by our finding of the FN1-EGF gene fusion, previously shown to be a characteristic feature of calcifying aponeurotic fibroma (CAF), in a morphologically typical case of lipofibromatosis that recurred showing features of CAF, we studied a cohort of 20 cases of lipofibromatosis for this and other genetic events. The cohort was composed of 14 males and 6 females (median age 3 years; range 1 month-14 years). All primary tumors showed classical lipofibromatosis morphology. Follow-up disclosed three local recurrences, two of which contained calcifying aponeurotic fibroma-like nodular calcifications in addition to areas of classic lipofibromatosis, and no metastases. By FISH and RNA sequencing, four cases were positive for FN1-EGF and one case each showed an EGR1-GRIA1, TPR-ROS1, SPARC-PDGFRB, FN1-TGFA, EGFR-BRAF, VCL-RET, or HBEGF-RBM27 fusion. FN1-EGF was the only recurrent fusion, suggesting that some cases of "lipofibromatosis" may represent calcifying aponeurotic fibroma lacking hallmark calcifications. Several of the genes involved in fusions (BRAF, EGFR, PDGFRB, RET, and ROS1) encode receptor tyrosine kinases (RTK), or ligands to the RTK EGFR (EGF, HBEGF, TGFA), suggesting a shared deregulation of the PI3K-AKT-mTOR pathway in a large subset of lipofibromatosis cases.

Inflammatory leiomyosarcoma is a distinct tumor characterized by near-haploidization, few somatic mutations, and a primitive myogenic gene expression signature.

Inflammatory leiomyosarcoma is a soft-tissue tumor resembling conventional leiomyosarcoma, but with a prominent intrinsic inflammatory component. Previous studies have suggested that inflammatory leiomyosarcoma differs genetically from leiomyosarcoma, but in-depth analyses are lacking. Here we provide a comprehensive picture of the genome and transcriptome of inflammatory leiomyosarcoma by combining cytogenetic, single-nucleotide polymorphism array, mRNA-sequencing, and whole-exome sequencing data. The results show that inflammatory leiomyosarcoma has a specific genetic profile characterized by near-haploidization with or without subsequent whole-genome doubling. Consistently, both parental copies of chromosomes 5 and 22 are preserved. Apart from recurrent mutation of the NF1 gene, additional somatic events that could serve as driver mutations were not found at either the nucleotide or the genome level. Furthermore, no fusion transcripts were identified. Global gene expression profiling revealed particularly prominent differential expression of genes, including ITGA7, MYF5, MYF6, MYOD1, MYOG, and PAX7, involved in muscle development and function, providing strong argument for grouping inflammatory leiomyosarcoma with myogenic sarcomas, rather than with myofibroblastic lesions. Combined with previously published data, there are now 10 cases of inflammatory leiomyosarcoma with confirmed near-haploid genotype. These patients differ from leiomyosarcoma patients in being younger (median 41 years), showing a male predominance (9:1), and few relapses (1 of 8 informative patients). Thus, the clinical, morphological, and genetic data provide compelling support for inflammatory leiomyosarcoma being a distinct subtype of myogenic tumors.

In-depth Genetic Analysis of Sclerosing Epithelioid Fibrosarcoma Reveals Recurrent Genomic Alterations and Potential Treatment Targets.

Purpose: Sclerosing epithelioid fibrosarcoma (SEF) is a highly aggressive soft tissue sarcoma closely related to low-grade fibromyxoid sarcoma (LGFMS). Some tumors display morphologic characteristics of both SEF and LGFMS, hence they are known as hybrid SEF/LGFMS. Despite the overlap of gene fusion variants between these two tumor types, SEF is much more aggressive. The current study aimed to further characterize SEF and hybrid SEF/LGFMS genetically to better understand the role of the characteristic fusion genes and possible additional genetic alterations in tumorigenesis.Experimental Design: We performed whole-exome sequencing, SNP array analysis, RNA sequencing (RNA-seq), global gene expression analyses, and/or IHC on a series of 13 SEFs and 6 hybrid SEF/LGFMS. We also expressed the FUS-CREB3L2 and EWSR1-CREB3L1 fusion genes conditionally in a fibroblast cell line; these cells were subsequently analyzed by RNA-seq, and expression of the CD24 protein was assessed by FACS analysis.Results: The SNP array analysis detected a large number of structural aberrations in SEF and SEF/LGFMS, many of which were recurrent, notably DMD microdeletions. RNA-seq identified FUS-CREM and PAX5-CREB3L1 as alternative fusion genes in one SEF each. CD24 was strongly upregulated, presumably a direct target of the fusion proteins. This was further confirmed by the gene expression analysis and FACS analysis on Tet-On 3G cells expressing EWSR1-CREB3L1Conclusions: Although gene fusions are the primary tumorigenic events in both SEF and LGFMS, additional genomic changes explain the differences in aggressiveness and clinical outcome between the two types. CD24 and DMD constitute potential therapeutic targets. Clin Cancer Res; 23(23); 7426-34. ©2017 AACR.

Soft tissue angiofibroma: Clinicopathologic, immunohistochemical and molecular analysis of 14 cases.

Soft tissue angiofibroma is rare and has characteristic histomorphological and genetic features. For diagnostic purposes, there are no specific antibodies available. Fourteen lesions (6 females, 8 males; age range 7-67 years) of the lower extremities (12) and trunk (2) were investigated by immunohistochemistry, including for the first time NCOA2. NCOA2 was also tested in a control group of other spindle cell lesions. The known fusion-genes (AHRR-NCOA2 and GTF2I-NCOA2) were examined using RT-PCR in order to evaluate their diagnostic value. Cases in which no fusion gene was detected were additionally analysed by RNA sequencing. All cases tested showed nuclear expression of NCOA2. However, this was not specific since other spindle cell neoplasms also expressed this marker in a high percentage of cases. Other variably positive markers were EMA, SMA, desmin and CD34. STAT6 was negative in the cases tested. By RT-PCR for the most frequently observed fusions, an AHRR-NCOA2 fusion transcript was found in 9/14 cases. GTF2I-NCOA2 was not detected in the remaining cases (n = 3). RNA sequencing revealed three additional positive cases; two harbored a AHRR-NCOA2 fusion and one case a novel GAB1-ABL1 fusion. Two cases failed molecular analysis due to poor RNA quality. In conclusion, the AHRR-NCOA2 fusion is a frequent finding in soft tissue angiofibroma, while GTF2I-NCOA2 seems to be a rare genetic event. For the first time, we report a GAB1-ABL1 fusion in a soft tissue angiofibroma of a child. Nuclear expression of NCOA2 is not discriminating when compared with other spindle cell neoplasms.

Scattered genomic amplification in dedifferentiated liposarcoma.

BACKGROUND: Atypical lipomatous tumor (ALT), well differentiated liposarcoma (WDLS) and dedifferentiated liposarcoma (DDLS) are cytogenetically characterized by near-diploid karyotypes with no or few other aberrations than supernumerary ring or giant marker chromosomes, although DDLS tend to have somewhat more complex rearrangements. In contrast, pleomorphic liposarcomas (PLS) have highly aberrant and heterogeneous karyotypes. The ring and giant marker chromosomes contain discontinuous amplicons, in particular including multiple copies of the target genes CDK4, HMGA2 and MDM2 from 12q, but often also sequences from other chromosomes. RESULTS: The present study presents a DDLS with an atypical hypertriploid karyotype without any ring or giant marker chromosomes. SNP array analyses revealed amplification of almost the entire 5p and discontinuous amplicons of 12q including the classical target genes, in particular CDK4. In addition, amplicons from 1q, 3q, 7p, 9p, 11q and 20q, covering from 2 to 14 Mb, were present. FISH analyses showed that sequences from 5p and 12q were scattered, separately or together, over more than 10 chromosomes of varying size. At RNA sequencing, significantly elevated expression, compared to myxoid liposarcomas, was seen for TRIO and AMACR in 5p and of CDK4, HMGA2 and MDM2 in 12q. CONCLUSIONS: The observed pattern of scattered amplification does not show the characteristics of chromothripsis, but is novel and differs from the well known cytogenetic manifestations of amplification, i.e., double minutes, homogeneously staining regions and ring chromosomes. Possible explanations for this unusual distribution of amplified sequences might be the mechanism of alternative lengthening of telomeres that is frequently active in DDLS and events associated with telomere crisis.

Frequent low-level mutations of protein kinase D2 in angiolipoma.

Tumours displaying differentiation towards normal fat constitute the most common subgroup of soft tissue neoplasms. A series of such tumours was investigated by whole-exome sequencing followed by targeted ultra-deep sequencing. Eighty per cent of angiolipomas, but not any other tumour type, displayed mutations in the protein kinase D2 (PRKD2) gene, typically in the part encoding the catalytic domain. The absence of other aberrations at the chromosome or RNA level suggests that PRKD2 mutations are critical for angiolipoma development. Consistently, the mutated PRKD2 alleles were present at low (3-15%) frequencies, indicating that only a subset of the tumour cells is affected. Indeed, by sequencing mature fat cells and other cells separately, the former typically showed the highest mutation frequencies. Thus, we hypothesize that altered PRKD2 signalling in the adipocytic cells drives tumourigenesis and, in agreement with its pivotal role in angiogenesis, induces the vessel formation that is characteristic for angiolipoma. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Myoepithelioma of bone with a novel FUS-POU5F1 fusion gene.

AIMS: Myoepithelial tumours of soft tissue are rare lesions with a broad morphological and clinical spectrum. Previous studies have found EWSR1 rearrangements in approximately half of all cases and PBX1, ZNF44 and POU5F1 have been identified as recurrent fusion partners. In bone, only a small number of myoepithelial tumours have been described. We investigated an intraosseous myoepithelioma of the sacrum in a 54-year-old man without EWSR1 rearrangement for the presence of other fusion genes. METHODS AND RESULTS: G-banding analysis, SNP-array and fluorescence in situ hybridisation suggested rearrangement of the FUS and POU5F1 genes. RT-PCR confirmed a chimeric in-frame transcript fusing FUS exon 5 to POU5F1 exon 2. The clinical course after en bloc resection was without recurrence or metastasis over a period of 87 months. CONCLUSION: We report a novel FUS-POU5F1 fusion gene in an intraosseous myoepithelioma of the sacrum. This case highlights that FUS can replace EWSR1 as the N-terminal transactivator in oncogenic fusion genes in myoepithelial tumours, similar to that which has previously been demonstrated in other tumour entities. Thus, in addition to EWSR1, also FUS needs to be considered as a potential fusion partner in the molecular work up of myoepithelial tumours.

Recurrent EWSR1-CREB3L1 gene fusions in sclerosing epithelioid fibrosarcoma.

Sclerosing epithelioid fibrosarcoma (SEF) and low-grade fibromyxoid sarcoma (LGFMS) are 2 distinct types of sarcoma, with a subset of cases showing overlapping morphologic and immunohistochemical features. LGFMS is characterized by expression of the MUC4 protein, and about 90% of cases display a distinctive FUS-CREB3L2 gene fusion. In addition, SEF is often MUC4 positive, but is genetically less well studied. Fluorescence in situ hybridization (FISH) studies have shown involvement of the FUS gene in the majority of so-called hybrid LGFMS/SEF and in 10% to 25% of sarcomas with pure SEF morphology. In this study, we investigated a series of 10 primary tumors showing pure SEF morphology, 4 cases of LGFMS that at local or distant relapse showed predominant SEF morphology, and 1 primary hybrid LGFMS/SEF. All but 1 case showed diffuse expression for MUC4. Using FISH, reverse transcription polymerase chain reaction, and/or mRNA sequencing in selected cases, we found recurrent EWSR1-CREB3L1 fusion transcripts by reverse transcription polymerase chain reaction in 3/10 pure SEF cases and splits and deletions of the EWSR1 and/or CREB3L1 genes by FISH in 6 additional cases. All 5 cases of LGFMS with progression to SEF morphology or hybrid features had FUS-CREB3L2 fusion transcripts. Our results indicate that EWSR1 and CREB3L1 rearrangements are predominant over FUS and CREB3L2 rearrangements in pure SEF, highlighting that SEF and LGFMS are different tumor types, with different impacts on patient outcome.

Recurrent chromosome 22 deletions in osteoblastoma affect inhibitors of the Wnt/beta-catenin signaling pathway.

Osteoblastoma is a bone forming tumor with histological features highly similar to osteoid osteoma; the discrimination between the tumor types is based on size and growth pattern. The vast majority of osteoblastomas are benign but there is a group of so-called aggressive osteoblastomas that can be diagnostically challenging at the histopathological level. The genetic aberrations required for osteoblastoma development are not known and no genetic difference between conventional and aggressive osteoblastoma has been reported. In order to identify recurrent genomic aberrations of importance for tumor development we applied cytogenetic and/or SNP array analyses on nine conventional and two aggressive osteoblastomas. The conventional osteoblastomas showed few or no acquired genetic aberrations while the aggressive tumors displayed heavily rearranged genomes. In one of the aggressive osteoblastomas, three neighboring regions in chromosome band 22q12 were homozygously deleted. Hemizygous deletions of these regions were found in two additional cases, one aggressive and one conventional. In total, 10 genes were recurrently and homozygously lost in osteoblastoma. Four of them are functionally involved in regulating osteogenesis and/or tumorigenesis. MN1 and NF2 have previously been implicated in the development of leukemia and solid tumors, and ZNRF3 and KREMEN1 are inhibitors of the Wnt/beta-catenin signaling pathway. In line with deletions of the latter two genes, high beta-catenin protein expression has previously been reported in osteoblastoma and aberrations affecting the Wnt/beta-catenin pathway have been found in other bone lesions, including osteoma and osteosarcoma.

A benign vascular tumor with a new fusion gene: EWSR1-NFATC1 in hemangioma of the bone.

The EWSR1 gene in chromosome band 22q12 is a promiscuous fusion partner involved in a vast array of tumors characterized by gene fusions. In this study, we report the finding of a new fusion gene, EWSR1-NFATC1, in a hemangioma of the bone; genetic rearrangements have not previously been described in this tumor type. Chromosome banding analysis showed a t(18;22)(q23;q12) translocation as the sole change. Fluorescence in situ hybridization mapping suggested the involvement of each of the 2 partner genes, and reverse transcriptase polymerase chain reaction revealed an in-frame EWSR1-NFATC1 transcript. NFATC1 has not previously been shown to be involved in a fusion chimera. However, NFATC2, encoding another member of the same protein family, is known to be a fusion partner for EWSR1 in a subgroup of Ewing sarcoma. Thus, our findings further broaden the spectrum of neoplasms associated with EWSR1 fusion genes, add a new partner to the growing list of EWSR1 chimeras, and suggest that chromosomal rearrangements of pathogenetic, and possibly also diagnostic, significance can be present in benign vascular bone tumors.