Xanthogranulomatous Epithelial Tumors and Keratin-Positive Giant Cell Rich Tumors of Soft Tissue and Bone: Two Sides of the Same Coin.

Xanthogranulomatous epithelial tumor is a recently described soft tissue tumor characterized by subcutaneous location, partial encapsulation, a xanthogranulomatous inflammatory cell infiltrate, and keratin-positive mononuclear cells. It shares some morphologic features with keratin-positive, giant cell-rich soft tissue tumors. Both have recently been shown to harbor HMGA2::NCOR2 fusions. The relationship between these tumors and their differential diagnosis with other osteoclast-containing soft tissue tumors is discussed.

Recurrent Fusion of the Genes for High-mobility Group AT-hook 2 (HMGA2) and Nuclear Receptor Co-repressor 2 (NCOR2) in Osteoclastic Giant Cell-rich Tumors of Bone.

BACKGROUND/AIM: Chimeras involving the high-mobility group AT-hook 2 gene (HMGA2 in 12q14.3) have been found in lipomas and other benign mesenchymal tumors. We report here a fusion of HMGA2 with the nuclear receptor co-repressor 2 gene (NCOR2 in 12q24.31) repeatedly found in tumors of bone and the first cytogenetic investigation of this fusion. MATERIALS AND METHODS: Six osteoclastic giant cell-rich tumors were investigated using G-banding, RNA sequencing, reverse transcription polymerase chain reaction, Sanger sequencing, and fluorescence in situ hybridization. RESULTS: Four tumors had structural chromosomal aberrations of 12q. The pathogenic variant c.103_104GG>AT (p.Gly35Met) in the H3.3 histone A gene was found in a tumor without 12q aberration. In-frame HMGA2-NCOR2 fusion transcripts were found in all tumors. In two cases, the presence of an HMGA2-NCOR2 fusion gene was confirmed by FISH on metaphase spreads. CONCLUSION: Our results demonstrate that a subset of osteoclastic giant cell-rich tumors of bone are characterized by an HMGA2-NCOR2 fusion gene.

Intramuscular Tenosynovial Giant Cell Tumor Harboring a Novel CSF1-CD96 Fusion Transcript.

Tenosynovial giant cell tumors typically arise in the synovium of joints, bursae, or tendon sheaths. They may occur in an intra- or extra-articular location and can be divided into localized and diffuse types. The neoplastic nature of the lesion has been supported by a recurrent CSF1 gene rearrangement in a small subset of lesional cells, of which the most common fusion partner is COL6A3. Herein, we report a case of intramuscular localized tenosynovial giant cell tumor harboring a novel CSF1-CD96 fusion transcript, thus expanding the molecular profile of this tumor.

Recurrent novel HMGA2-NCOR2 fusions characterize a subset of keratin-positive giant cell-rich soft tissue tumors.

Giant cell tumors of soft tissue (GCT-ST) are rare low-grade neoplasms that were at one time thought to represent the soft tissue counterparts of GCT of bone (GCT-B) but are now known to lack the H3F3 mutations characteristic of osseous GCT. We present six distinctive giant cell-rich soft tissue neoplasms that expressed keratins and carried a recurrent HMGA2-NCOR2 gene fusion. Patients were five females and one male aged 14-60 years (median, 29). All presented with superficial (subcutaneous) masses that were removed by conservative marginal (3) or wide (2) local excision. The tumors originated in the upper extremity (2), lower extremity (2), head/neck (1), and trunk (1). Five patients with follow-up (median, 21 months; range, 14-168) remained disease-free. Grossly, all tumors were well-demarcated but not encapsulated with variable lobulation. Histologically, they were composed of bland plump epithelioid or ovoid to spindled mononuclear cells admixed with evenly distributed multinucleated osteoclast-type giant cells. Foci of stromal hemorrhage and hemosiderin were seen in all cases. The mitotic activity ranged from 2 to 14/10 high power fields (median: 10). Foci of necrosis and vascular invasion were seen in one case each. The mononuclear cells were immunoreactive with the AE1/AE3 keratin cocktail and less frequently/less diffusely for K7 and K19 but lacked expression of other lineage-associated markers. RNA-based next-generation sequencing revealed an HMGA2-NCOR2 fusion in all tumors. None of the keratin-negative conventional GCT-ST showed the HMGA2-NCOR2 fusion (0/7). Metaplastic bone (4/9) and SATB2 expression (3/4) were frequent in keratin-negative conventional GCT-ST but were lacking in keratin-positive HMGA2-NCOR2 fusion-positive tumors. The distinctive immunophenotype and genotype of these tumors strongly suggest that they represent a discrete entity, differing from conventional GCT-ST and other osteoclast-rich morphologic mimics. Their natural history appears favorable, although a study of additional cases and longer follow-up are warranted.

Prognostic role of PD-L1 and immune-related gene expression profiles in giant cell tumors of bone.

Giant cell tumor of bone (GCTB) is a locally aggressive and rarely metastatic tumor, with a relatively unpredictable clinical course. A retrospective series of 46 GCTB and a control group of 24 aneurysmal bone cysts (ABC) were selected with the aim of investigating the PD-L1 expression levels and immune-related gene expression profile, in correlation with clinicopathological features. PD-L1 and Ki67 were immunohistochemically tested in each case. Furthermore, comprehensive molecular analyses were carried out using NanoString technology and nCounter PanCancer Immune Profiling Panel, and the gene expression results were correlated with clinicopathological characteristics. PD-L1 expression was observed in 13/46 (28.3%) GCTB (and in 1/24, 4.2%, control ABC, only) and associated with a shorter disease free interval according to univariate analysis. Moreover, in PD-L1-positive lesions, three genes (CD27, CD6 and IL10) were significantly upregulated (p < 0.01), while two were downregulated (LCK and TLR8, showing borderline significance, p = 0.06). Interestingly, these genes can be related to maturation and immune tolerance of bone tissue microenvironment, suggesting a more immature/anergic phenotype of giant cell tumors. Our findings suggest that PD-L1 immunoreactivity may help to select GCTB patients with a higher risk of recurrence who could potentially benefit from immune checkpoint blockade.

What is new about the molecular genetics in matrix-producing soft tissue tumors? -The contributions to pathogenetic understanding and diagnostic classification.

Soft tissue tumors encompass a wide variety of mesenchymal neoplasms exhibiting diverse clinical, pathologic, and molecular features. Among these, osteoid and/or chondroid matrix deposition in some soft tissue tumors represents a noticeable characteristic. Unlike matrices present in bone tumors where they likely reveal the respective cells of origin (i.e., osteoblastic or chondroblastic precursors), those existing in soft tissue tumors more often denote a metaplastic phenomenon and reflect the diversity of differentiation these tumors can display. While many soft tissue tumor types can occasionally harbor metaplastic bone or cartilage as an incidental component or heterologous differentiation, in some other tumor types, the production of these matrices is a frequent and distinctive, if not diagnostic, feature. This review focuses on the latter tumor types where emerging immunohistochemical and molecular evidence has significantly improved our understanding of their respective pathogenesis and histopathological spectra. These tumor types include ossifying fibromyxoid tumor, phosphaturic mesenchymal tumor, synovial chondromatosis, soft tissue chondroma, calcifying aponeurotic fibroma, giant cell tumor of soft tissue, myositis ossificans and related diseases, mesenchymal chondrosarcoma, and extraskeletal osteosarcoma.

Making sense of giant cell lesions of the jaws (GCLJ): lessons learned from next-generation sequencing.

Next-generation sequencing has revealed mutations in several bone-related lesions and was recently used to uncover the genetic basis of giant cell lesions of the jaws (GCLJ). Consistent with their benign nature, GCLJ show a low tumor mutation burden. They also harbor somatic, heterozygous, mutually exclusive mutations in TRPV4, KRAS, or FGFR1. These signature mutations occur only in a subset of lesional cells, suggesting the existence of a 'landscaping effect', with mutant cells inducing abnormal accumulation of non-mutant cells that form the tumor mass. Osteoclast-rich lesions with histological similarities to GCLJ can occur in the jaws sporadically or in association with genetically inherited syndromes. Based on recent results, the pathogenesis of a subgroup of sporadic GCLJ seems closely related to non-ossifying fibroma of long bones, with both lesions sharing MAPK pathway-activating mutations. In this review, we extrapolate from these recent findings to contextualize GCLJ genetics and we highlight the therapeutic implications of this new information. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Cytogenetic Single-Institution Analysis: 101 Consecutive Cases of Soft-Tissue Tumors of the Extremities.

We summarize the results and clinical usefulness of cytogenetic analysis that is routinely performed for musculoskeletal tumors. We performed cytogenetic analysis and traditional histologic evaluation on 101 (51 malignant/ 50 benign) consecutive tumors that were surgically excised. The successful culture rate for cytogenetic analysis was 86% (87/101). Fifty-four percent (25/46) of clearly malignant tumors that were successfully cultured demonstrated significant clonal abnormalities. Fifty-one percent (21/41) of benign tumors that were cultured had significant cytogenetic clonal aberrations. Increased cellular ploidy (> 50 chromosomes/cell) was demonstrated in 14/46 malignant and 1/41 benign tumors that were successfully cultured. Hyperploidy was highly correlated with malignancy (p < 0.001); the only "benign" tumor was a multiply recurrent and giant cell, demonstrating histologic changes consistent with early sarcomatous transformation. As expected, cytogenetic abnormalities frequently occurred in malignant tumors. Surprisingly, almost half of the benign tumors had significant clonal cytogenetic aberrations. Consistent findings of extra chromosomes 5 and 7 in samples of pigmented villonodular synovitis strongly favored a neoplastic origin for this condition. Although the presence or absence of cytogenetic aberrations cannot be used to determine malignant potential, increased cellular ploidy is highly indicative of malignancy. Modern molecular genetics have become more popular, but cytogenetic analysis can be useful for classifying the malignant potential of recurrent and difficult to diagnose tumors of the musculoskeletal system.

ZNF687 mutations are frequently found in pagetic patients from South Italy: implication in the pathogenesis of Paget's disease of bone.

Paget's disease of bone (PDB) is a skeletal disorder whose molecular basis is not fully elucidated. However, 10% of patients show a familial PDB and 35% of them carry mutations in the SQSTM1 gene. We recently reported a founder mutation (p.Pro937Arg) in the ZNF687 gene, underlying PDB complicated by giant cell tumor (GCT/PDB) and rarely occurring in PDB patients without neoplastic degeneration. Since 80% of Italian GCT/PDB patients derive from Avellino, we hypothesized that ZNF687 mutation rate was higher in this region than elsewhere. Interestingly, our molecular analysis on 30 PDB patients showed that 33% hosted ZNF687 mutations, with the p.Pro937Arg identified in 8 familial cases. Two novel ZNF687 mutations (p.Pro665Leu and p.Gln784Glu) were detected in 2 sporadic patients. Only 2 subjects were positive for the p.Pro392Leu mutation in SQSTM1. ZNF687-mutated patients showed a severe PDB, with a remarkable number of affected sites. in vitro studies revealed that the ZNF687-mutant osteoclasts appeared as giant sized with up to 150 nuclei, never described in PDB. Finally, we also confirmed the causality of the p.Pro937Arg mutation in 4 additional GCT/PDB cases deriving from the same geographic area, indicating that PDB and GCT/PDB represent 2 sides of the same coin.

Phenotypic and molecular differences between giant-cell tumour of soft tissue and its bone counterpart.

AIMS: Giant-cell tumour (GCT) of soft tissue (GCT-ST) is a primary soft tissue neoplasm that is histologically similar to GCT of bone (GCT-B). Recently, it has been reported that >90% of GCT-Bs have a driver mutation in the H3F3A gene. As the relationship between GCT-ST and GCT-B is unclear, the aim of this study was to compare a series of GCT-STs and GCT-Bs with regard to the presence of H3F3A mutations and several immunophenotypic markers. METHODS AND RESULTS: Eight GCT-STs were retrieved from our institutional archives. Fifteen GCT-Bs served as controls. Direct sequencing for H3F3A mutations in coding regions between codons 1 and 42, including the hotspot codons (28, 35, and 37), was performed on DNA extracted from formalin-fixed paraffin-embedded tissue. Tumours were studied immunohistochemically for the expression of CD14, CD33, RANKL, RANK, p63, and the osteoblastic markers SATB2 and RUNX2. None of the seven GCT-STs that could be analysed showed H3F3A mutations, whereas 14 GCT-Bs (93.3%) were mutated. All eight GCT-STs were positive for RANK and RUNX2, whereas RANKL and SATB2 were detected in only two cases (25%). CD14 was detected only in mononuclear elements, whereas multinucleated giant cells and a proportion of the mononuclear population expressed CD33. Few mononuclear cells of GCT-STs expressed p63. In comparison, GCT-Bs showed higher expression of p63 (14 of 15 cases with >50% of positive mononuclear cells), RANKL, and SATB2, whereas CD14, CD33, RANK and RUNX2 were similarly expressed. CONCLUSIONS: Although GCT-ST and GCT-B are similar in histological appearance, our results indicate that they are immunophenotypically and genetically distinct.

3-Dimensional micropillar drug screening identifies FGFR2-IIIC overexpression as a potential target in metastatic giant cell tumor.

We established two patient derived tumor cells (PDCs) from right and left pulmonary metastatic lesions respectively of a patient with giant cell tumor. At that time, patient-derived tumor cells from right and left surgical specimens were collected and cultured. High-throughput screening (HTS) for 24 drugs was conducted with a micropillar/microwell chip platform using giant cell tumor PDCs. Using 6 doses per drug in 6 replicates for giant cell tumor PDCs, the dose response curves and corresponding IC50 values were calculated from the scanned images using the S+ Chip Analyzer. A sensitive response was more significantly achieved for AZD4547 (FGFR2 inhibitor) in giant cell tumor PDCs originated from the right pulmonary nodule under the micropillar/microwell chip platform using 3D culture. This sensitivity was consistent with the target expression patterns of giant cell tumor PDCs (FGFR2-IIIC mRNA expression in giant cell tumor PDCs originated from the right pulmonary nodule was increased significantly as compared to those originated from left). However, in a conventional 2D cultured MTT assay, there was no difference for IC50 values of AZD4547 between giant cell tumor PDCs originated from right and left pulmonary nodules. An HTS platform based on 3D culture on micropillar/microwell chips and PDC models could be applied as a useful preclinical tool to evaluate the intrapatient tumor/response heterogeneity. This platform based on 3D culture might reflect far better the relation between the tumor-biology and the matched targeted agent as compared to a conventional 2D cultured MTT assay.

Giant cell tumor of soft tissue is genetically distinct from its bone counterpart.

Giant cell tumors of bone are locally aggressive bone neoplasms with a predilection for young adults. Histologically, they are composed of histiocytoid to spindled mononuclear cells, admixed with numerous large osteoclastic giant cells. Giant cell tumors of soft tissue are rare tumors that bear striking histological resemblance to giant cell tumors of bone and might be regarded as a soft tissue analog thereof. Point mutations of the H3F3A gene (coding for a histone H3.3 protein) at the Gly34 codon, mostly G34W resulting from a GGG>TGG nucleotide change, have recently been identified in a vast majority of giant cell tumors of bone. To delineate the possible pathogenic linkage between both tumor types, we analyzed the H3F3A genotypes in a series of 15 giant cell tumors of soft tissue by Sanger sequencing and found no mutation in any case. We then sequenced cognate histone H3 genes with an identical nucleotide sequence ('GGG') at the codon Gly34, including the H3F3B, H3F3C, HIST2H3A, HIST2H3C, and HIST2H3D genes, and no somatic mutation was detected. These results reveal that giant cell tumors of soft tissue are probably genetically distinct from their bone counterparts and suggest that they might be pathogenically unrelated. Given the prominence of non-neoplastic cells in these tumors and the limitations of the current study, however, analyses using more sensitive techniques might be required to solve the issue.

ZNF687 Mutations in Severe Paget Disease of Bone Associated with Giant Cell Tumor.

Paget disease of bone (PDB) is a skeletal disorder characterized by focal abnormalities of bone remodeling, which result in enlarged and deformed bones in one or more regions of the skeleton. In some cases, the pagetic tissue undergoes neoplastic transformation, resulting in osteosarcoma and, less frequently, in giant cell tumor of bone (GCT). We performed whole-exome sequencing in a large family with 14 PDB-affected members, four of whom developed GCT at multiple pagetic skeletal sites, and we identified the c.2810C>G (p.Pro937Arg) missense mutation in the zinc finger protein 687 gene (ZNF687). The mutation precisely co-segregated with the clinical phenotype in all affected family members. The sequencing of seven unrelated individuals with GCT associated with PDB (GCT/PDB) identified the same mutation in all individuals, unravelling a founder effect. ZNF687 is highly expressed during osteoclastogenesis and osteoblastogenesis and is dramatically upregulated in the tumor tissue of individuals with GCT/PDB. Interestingly, our preliminary findings showed that ZNF687, indicated as a target gene of the NFkB transcription factor by ChIP-seq analysis, is also upregulated in the peripheral blood of PDB-affected individuals with (n = 5) or without (n = 6) mutations in SQSTM1, encouraging additional studies to investigate its potential role as a biomarker of PDB risk.

Imatinib promotes apoptosis of giant cell tumor cells by targeting microRNA-30a-mediated runt-related transcription factor 2.

Giant cell tumor (GCT) is an aggressive type of bone tumor consisting of multinucleated osteoclast-like giant cells. Imatinib is a selective inhibitor for certain type III tyrosine kinase receptor family members with a variety of beneficial effects. The purpose of the present study was to determine the therapeutic potential and underlying mechanism of imatinib against GCT. In the present study, cell viability and apoptosis in GCT were analyzed using the MTT assay, flow cytometry and DAPI staining assay. Caspase-3 and -9 activity in GCT cells were analyzed with colorimetric assay kits. In addition, the expression levels of runt-related transcription factor 2 (RunX2) protein and microRNA-30a (miR-30a) in GCT cells were detected using western blotting and quantitative polymerase chain reaction, respectively. Results from the present study demonstrated that imatinib treatment inhibited cell viability, increased cell apoptosis, and significantly promoted caspase-3 and -9 activity in GCT. In addition, imatinib treatment decreased the RunX2 protein expression level. Notably, imatinib was demonstrated to increase miR-30a expression. However, upregulation of miR-30a expression reduced the RunX2 protein expression level, and downregulation of miR-30a expression reversed the anticancer effect of imatinib on GCT, increasing the expression level of RunX2 protein in GCT. The results of the present study indicate that imatinib promotes apoptosis of GCT cells by targeting the miR-30a-mediated RunX2 signaling pathway.

Quantitative analysis of the concentrations of IGFs and several IGF-binding proteins in a large fibrous abdominal tumor and the circulation of a patient with hypoglycemia.

The syndrome of nonislet cell tumor induced hypoglycemia (NICTH) represent extreme cases of excessive expression and production of incompletely processed high-molecular-mass pro-IGF-II forms (big IGF-II) by an often large tumor. Tumor-derived big IGF-II is responsible for enhanced insulin-like effects in the body through complicated mechanisms, leading to hypoglycemia. Case studies on NICTH usually focus on measurements of diagnostic parameters in the circulation of patients. Some studies have also reported on qualitative immunohistochemical analysis of tumor tissue, in particular with respect to the expression of IGF-II at the mRNA or protein level. However, quantitative data on the concentrations of IGFs and IGFBPs in tumor specimen causing NICTH, in relation to their corresponding plasma levels are lacking. Such an analysis would provide an estimate of the total potential of (big) IGF-II retained by the tumor and more insight in the relative levels of different IGFBPs and their origin in the circulation, that is, systemically induced by tumor related factors or directly tumor-derived. Here we investigated quantitatively the levels of IGFs and IGFBPs in a large, 1.76 kg weighing, solitary fibrous tumor from a typical case of NICTH using highly specific immunometric assays. Besides a high level of big IGF-II, patient's plasma also contained increased levels of both IGFBP-2 and -6 which declined after removal of the tumor. These IGFBPs have a higher affinity for (pro-) IGF-II than IGF-I and exhibit intrinsic IGF-independent bioactivities. Tumor tissue contained high amounts of big IGF-II and IGFBP-6, exceeding that in patient's circulation many-fold. A relatively low tumor content of IGFBP-2 was found suggesting that the preoperative high levels in plasma were attributable to systemic mechanisms. The background literature and possible implications of these findings are briefly discussed. Based on the present results we postulate that tumor tissue is not the source of the elevated levels of IGFBP-2 often seen in NICTH patients. Large tumors that cause NICTH can produce IGFBP-6 leading to enhanced levels of this IGFBP in the circulation. Hence, the measurement of IGFBP-6 in plasma may serve as an additional marker of this disease pattern.

Diffuse-type tenosynovial giant cell tumor with t(1;17)(p13;p13) and trisomy 5.

Diffuse-type tenosynovial giant cell tumor (TSGCT) is a locally aggressive neoplasm that primarily affects the synovium and tendon sheath in young adults. Rearrangement of chromosome band 1p13 is now considered a characteristic genetic feature of TSGCT, with the most frequent chromosomal alteration t(1;2)(p13;q37). Here, we describe a unique cytogenetic finding of diffuse-type TSGCT arising in the ankle of an 18-year-old woman. Magnetic resonance imaging demonstrated an ill-defined juxta-articular mass with decreased signal intensity on both T1- and T2-weighted images. Contrast-enhanced T1-weighted images showed intense enhancement of the mass. Open complete resection was performed. Histologically, the tumor was composed of mononuclear cells admixed with multi-nucleated osteoclast-like giant cells, foam cells, siderophages and inflammatory cells. Cytogenetic analysis revealed a reciprocal translocation involving chromosomes 1 and 17, concomitant with a few other numerical and structural alterations. In addition, trisomy 5 as the sole anomaly was identified in two metaphase cells. To the best of our knowledge, this is the first report of this neoplasm with t(1;17)(p13;p13).

MiR-126-5p regulates osteolysis formation and stromal cell proliferation in giant cell tumor through inhibition of PTHrP.

Parathyroid hormone-related protein (PTHrP) has been identified to play a crucial role in osteolysis formation and stromal cell (GCTSC) proliferation in giant cell tumor (GCT). MiR-126-5p is an intronic miRNA identified as tumor suppressor in many tumors, but its role in GCT is poorly understood. We found that miR-126-5p was decreased in GCT and could directly regulate PTHrP expression. Furthermore, miR-126-5p could control osteoclast (OC) differentiation, GCTSC proliferation and osteolysis formation in GCT through negative regulation of PTHrP. Thus, these results suggest that miR-126-5p could directly target PTHrP and have a tumor suppressor function in GCT.