Histological and immunohistochemical features and genetic alterations in the malignant progression of giant cell tumor of bone: a possible association with TP53 mutation and loss of H3K27 trimethylation.

In rare cases, giant cell tumor of bone (GCTB) can undergo primary or secondary malignant transformation to malignant giant cell tumor of bone (MGCTB), but the details of the molecular alterations are still unclear. The present study aimed to elucidate the clinicopathologic and molecular features of MGCTBs based on immunohistochemistry, fluorescence in situ hybridization (FISH) and next generation sequencing (NGS) of nine MGCTBs (five primary and four secondary). Seven (78%) of 9 MGCTBs were immunohistochemically positive for H3.3 G34W. In two (22%) patients, although GCTB components were focally or diffusely positive for H3.3 G34W, their malignant components were entirely negative for H3.3 G34W, which was associated with heterozygous loss of H3F3A by FISH. NGS on four MGCTBs revealed pathogenic mutations in TP53 (n = 3), EZH2 (n = 1) and several other genes. Immunohistochemical analysis of the nine MGCTBs confirmed the p53 nuclear accumulation (n = 5) and loss of H3K27me3 expression (n = 3) and showed that they were mutually exclusive. In addition, four (80%) of five cases of pleomorphic or epithelioid cell-predominant MGCTBs were positive for p53, while three (75%) of four cases of spindle cell-predominant MGCTBs were negative for trimethylation at lysine 27 of histone 3 (H3K27me3). The results suggested that p53 alteration and dysfunction of histone methylation as evidenced by H3K27me3 loss may play an important role in the malignant progression of GCTB, and might contribute to the phenotype-genotype correlation in MGCTB. The combined histologic, immunohistochemical and molecular information may be helpful in part for the diagnosis of challenging cases.

Combined fibrinogen and neutrophil-lymphocyte ratio as a biomarker in predicting recurrence of giant cell tumor of bone.

Aims: The present study investigated the combined clinical significance of fibrinogen and neutrophil-lymphocyte ratio (F-NLR) in predicting postoperative recurrence of giant cell tumor of bone. Methods: A total of 113 participants were included in this retrospective study to examine the effects of inflammatory factors on postoperative tumor recurrence. Results: The high-score F-NLR group was significantly associated with larger tumor size (p = 0.001), advanced tumor stage (p = 0.018), wide resection (p = 0.004) and greater local recurrence (p = 0.014). Univariate and multivariate survival analyses revealed that F-NLR (p = 0.035) remained an independent factor influencing tumor recurrence rates. Conclusions: This study reveals that the F-NLR score is a promising blood biomarker for predicting giant cell tumor recurrence.

Giant cell tumor of bone (GCT) is predominantly regarded as an intermediate, locally destructive but rarely metastasizing tumor with recurrence potential and peak incidence in the second to fourth decades of life. The treatment of GCT is often difficult due to local recurrence. Therefore, a new indicator is urgently needed to predict postoperative recurrence more accurately in patients with GCT. The preoperative combined fibrinogen and neutrophil­lymphocyte ratio as a predictor of tumor recurrence and prognosis in GCT patients has been assessed. The present study is the first to demonstrate that a grading system based on the fibrinogen and neutrophil­lymphocyte ratio score is an easily determined, meaningful and reproducible biomarker for predicting recurrence in GCT patients.

Cytodiagnosis of giant cell tumour presenting at unusual age and site with review of literature.

Giant cell tumour (GCT), also known as osteoclastoma, is an osteolytic tumour. It involves the epiphyseal and metaphyseal regions of long bones in adults. On rare occasions, these may occur in paediatric patients, and may involve uncommon locations such as the sternum, pelvis and, particularly infrequently, rib bones. We present a rare case of GCT in the rib of a child, diagnosed on fine needle aspiration.

Clinicopathologic and molecular features of denosumab-treated giant cell tumour of bone (GCTB): Analysis of 21 cases.

GCTB is an osteolytic, locally-aggressive, rarely-metastasizing tumour, characterized by abundance of osteoclast-like giant cells, induced by neoplastic mononuclear cells expressing high-levels of the receptor activator of nuclear factor Kappa-B ligand (RANKL), a mediator of osteoclast activation. Although the mainstay of treatment is complete tumour removal with preservation of bone, therapy with denosumab, an inhibitor of RANKL, has been introduced for selected cases. OBJECTIVES: Denosumab-treated GCTB (DT-GCTB) was reported to show a wide spectrum of histological changes such as depletion of osteoclast-like giant cells and intralesional bone deposition, which may lead to diagnostic difficulties. We investigated clinicopathologic and molecular features of DT-GCTB, matched with pre-therapy samples. PARTICIPANTS: 21 cases were included (13 females, 8 males), aged 15 to 64 (median, 30 years). RESULTS: DT-GCTB showed development of sclerotic neocortex and varying degrees of osteosclerosis radiographically. Marked depletion of giant cells, different degree of ossification, fibrosis, and proliferation of mononuclear cells was observed. Staining for H3.3G34W was positive in mononuclear cells in 19 cases (90.5%), while one negative case was positive for H3.3G34V. H3F3A G34W mutation was confirmed in 17 of 19 cases (89.5%), corresponding to nuclear staining with H3.3 G34W antibody. G34L mutation was detected in one G34W negative case, in which H3.3 G34V nuclear positive staining was observed, possibly due to cross-reaction. CONCLUSIONS: Post-therapy tumours still exhibit a similar mutation profile, while significantly differing from classic GCTB morphologically. Correlation with history of denosumab administration, awareness of features of DT-GCTB, IHC and molecular studies for histone H3 mutations are important in its assessment.

Malignant Transformation of Giant Cell Tumour of Bone: A Review of Literature and the Experience of a Referral Centre.

Giant cell tumour of bone (GCTB) is a benign, locally aggressive primary bone neoplasm that represents 5% of all bone tumours. The principal treatment approach is surgery. Although generally GCTB is considered only a locally aggressive disease, it can metastasise, and lung metastases occur in 1-9% of patients. To date, only the use of denosumab has been approved as medical treatment for GCTB. Even more rarely, GCTB undergoes sarcomatous transformation into a malignant tumour (4% of all GCTB), but history of this malignant transformation is unclear and unpredictable. Considering the rarity of the event, the data in the literature are few. In this review, we summarise published data of GCTB malignant transformation and we analyse three cases of malignant transformation of GCTB, evaluating histopathology, genetics, and radiological aspects. Despite the rarity of this event, we conclude that a strict follow up is recommended to detect early malignant transformation.

Diagnostic Utility of Genetic and Immunohistochemical H3-3A Mutation Analysis in Giant Cell Tumour of Bone.

To validate the reliability and implementation of an objective diagnostic method for giant cell tumour of bone (GCTB). H3-3A gene mutation testing was performed using two different methods, Sanger sequencing and immunohistochemical (IHC) assays. A total of 214 patients, including 120 with GCTB and 94 with other giant cell-rich bone lesions, participated in the study. Sanger sequencing and IHC with anti-histone H3.3 G34W and G34V antibodies were performed on formalin-fixed, paraffin-embedded tissues, which were previously decalcified in EDTA if needed. The sensitivity and specificity of the molecular method was 100% (95% CI: 96.97-100%) and 100% (95% CI: 96.15-100%), respectively. The sensitivity and specificity of IHC was 94.32% (95% CI: 87.24-98.13%) and 100% (95% CI: 93.94-100.0%), respectively. P.G35 mutations were discovered in 2/9 (22.2%) secondary malignant GCTBs and 9/13 (69.2%) GCTB after denosumab treatment. We confirmed in a large series of patients that evaluation of H3-3A mutational status using direct sequencing is a reliable tool for diagnosing GCTB, and it should be incorporated into the diagnostic algorithm. Additionally, we discovered IHC can be used as a screening tool. Proper tissue processing and decalcification are necessary. The presence of the H3-3A mutation did not exclude malignant GCTB. Denosumab did not eradicate the neoplastic cell population of GCTB.

H3F3A-mutated giant cell tumour of bone without giant cells-clinical presentation, radiology and histology of three cases.

AIMS: Giant cell tumour of bone (GCTB) is histologically defined as a lesion containing reactive giant cells and a neoplastic mononuclear cell population; in up to 92% of cases, GCTB is characterised by a specific mutation of the histone gene H3F3A. The cellular composition ranges from giant-cell-rich to giant-cell-poor. The diagnosis of GCTB can be challenging, and several other lesions need to be excluded, e.g. aneurysmal bone cysts, non-ossifying fibromas, chondroblastomas, brown tumours, and giant-cell-rich osteosarcomas. Our aim was to analyse the clinical history, imaging, molecular pathology and histology of three H3F3A-mutated bone tumours without detectable giant cells. None of the patients received denosumab therapy. METHODS AND RESULTS: Diagnostic material was obtained by curettage or resection and/or biopsy. Common histomorphological features of all three reported lesions were fibrocytic, oval cells in a background of osteoid and an absence of multinuclear giant cells as confirmed with CD68 immunohistochemistry. We used immunohistochemistry and Sanger sequencing to demonstrate positivity for the H3.3 p.G34W mutation. Differential diagnoses were systematically excluded on the basis of histomorphology, immunohistochemistry, and fluorescence in-situ hybridisation. The imaging (radiography, computed tomography, and magnetic resonance imaging) for all three cases is presented and discussed. CONCLUSIONS: We believe that these GCTBs without giant cells expand one end of the heterogeneous range of GCTB. Because of the lack of giant cells, correct diagnosis of GCTB is challenging or even impossible on histological grounds alone. In these cases, detection of the characteristic H3F3A mutation (G34W-specific antibody RM263 or sequencing) is extremely helpful for diagnosing those lesions without giant cells as giant cell tumours of bone.

[DNA sequencing of H3F3A mutations in H3.3 immunohistochemistry-negative giant cell tumors of bone].

Objective: To investigate the subtypes of H3F3A DNA mutation in H3.3 immunohistochemistry (IHC) negative giant cell tumors of bone (GCTB). Methods: IHC expression of G34W mutated protein was evaluated in 181 cases GCTB. In H3.3 IHC negative cases, Sanger DNA sequencing analysis was used to detect the subtypes H3F3A mutations. Results: Overall, 164 (90.61%) cases of GCTB showed nuclear expression of H3.3, and 17 cases were negative. These 17 H3.3 negative cases were subjected to Sanger DNA sequencing analysis; results showed that eight presented rare mutation subtypes occurring at glycine 34 to leucine (G34L, 3/181, 1.66%), glycine 34 to valine (G34V, 3/181, 1.66%) and glycine 34 to arginine (G34R, 2/181, 1.10%), and the other nine cases were wild type (glycine 34, 9/181, 4.97%). Sanger DNA sequencing analysis confirmed the absence of G34W mutation in the H3.3 negative cases. Combining IHC and DNA sequencing analysis increased the detection rate of H3F3A mutation in the GCTB to 95.03%. Conclusions: H3.3 IHC could detect H3F3A G34W mutation in GCTB, but not for other rare mutation and wild types loci.

Huge aneurysmal bone cyst secondary to giant cell tumor of the hand phalanx: a case report and related literature.

BACKGROUND: Aneurysmal bone cyst (ABC) secondary to Giant Cell Tumor of bone (GCT) is a rare lesion, of which the incidence is about 0.011 to 0.053 per 100,000 every year. There are only a few previous case reports, and most of them occur in the spine, long bones or flat bones. CASE PRESENTATION: We report one case of a patient who complained of "progressive enlargement of the mass on right-hand fifth finger for 5 years with ulceration for 6 months". After the imaging examination in our hospital, it was diagnosed as a "huge bone tumor on the proximal phalanx of the right-hand fifth finger", then wide excision and amputation of the fifth finger were made. The pathological examination diagnosed the mass as aneurysmal bone cyst secondary to giant cell tumor, 13 × 8 × 6 cm3, with no local infiltration observed. No recurrence and metastasis occurred 18 months after the operation, and the patient recovered well. CONCLUSION: In this report, we discuss the etiology, diagnosis, differentiation, and management of Aneurysmal bone Cyst secondary to Giant Cell Tumor of bone, and review previous case studies.

Role of (Neo)adjuvant Denosumab for Giant Cell Tumor of Bone.

OPINION STATEMENT: Denosumab is a RANK ligand inhibitor approved for the treatment of giant cell tumor of bone. While the role of denosumab in the setting of advanced and unresectable disease is well established, its role in surgically resectable disease is currently under discussion. Several prospective and retrospective series on neoadjuvant therapy in potentially resectable tumor with high morbidity surgery reported a relapse rate of 10-20% after resection and 30-40% after curettage. At the same time, less morbid surgery has obvious clinical advantages for the patient, and several studies have shown the efficacy of denosumab in downgrading of the surgical procedure. Currently, the role of neoadjuvant denosumab in operable GCTB is limited to selected cases in which a diffuse reactive bone formation and peripheral ossification can make an easier surgical procedure, for example, in tumors with a large soft tissue component. A planned resection may become less morbid when preoperative denosumab is administered. Whenever a segmental resection is thought to be indicated at diagnosis, denosumab may be considered in the neoadjuvant setting. A preoperative course of 6 months is considered safe and effective. Two case scenarios are presented and critically discussed. Because of the high recurrence rates after denosumab treatment followed by curettage, we discourage the use of denosumab when curettage is considered feasible. In this setting, a short course of preoperative denosumab (2-6 months) may be considered for highly selected cases, for example in pathological fractures. The role of adjuvant denosumab needs further investigation. Long-term disease control has been reported in case of non-surgical lesions, even after treatment interruption, but there is no consensus on ideal treatment duration and dosage for these scenarios. In all cases, multidisciplinary discussion with oncology, pathologist, radiologist, and surgeons is mandatory. Patient's comorbidities, dental conditions, and preferences, including family planning, should always be taken into account.

Clinical Value of Differential lncRNA Expressions in Diagnosis of Giant Cell Tumor of Bone and Tumor Recurrence.

BACKGROUND: There is currently no clinical biomarker for the early diagnosis of giant cell tumor of bone. Long-chain non-coding RNAs (lncRNAs) have a wide range of important gene regulatory functions and play an important role in the occurrence and development of various malignant tumors. This study mainly screened the differential expression of lncRNAs in patients with giant cell tumor of bone by gene chip technology, verified the biological function. We tried to establish a reference basis for early diagnosis of tumor and prediction of tumor recurrence. METHODS: From September 2018 to September 2019, we randomly selected 20 cases of primary giant cell tumor of bone and 20 cases of recurrent giant cell tumor of bone, and 20 cases of bone trauma tissue. First, the differential expression of incRNAs in the bone tissue of the patients was evaluated via utilizing gene chip technology. The gene chip was Human LncRNA Array v 3.0 (8 x 60 K) was completed by Shanghai Kangcheng Biotechnology Co., Ltd. The DAVID online analysis platform was used to analyze the differentially expressed genes by GO and KEGG pathways. The target lncRNAs were screened; real-time quantitative PCR (qRT-PCR) was used to verify the relative expression levels of target lncRNAs in bone tissue and serum of three groups of patients. RESULTS: Using gene chip technology screening, fold-change (FC) value > 2.0 was used as standard. A total of 1,254 differentially expressed lncRNAs were detected of which 896 were up-regulated and 358 were down-regulated. Additionally, a total of 106 differentially expressed lncRNAs were detected with FC values > 10.0. Among these, 72 lncRNAs were upregulated and 34 lncRNAs were downregulated. We then selected two lncRNAs with up-regulation and down-regulation with the largest fold difference. qRT-PCR analytical results showcased that the expression of AK124776 in bone tissue and serum of patients in the recurrent group was significantly higher than that of the initial group and the normal group. Conversely, for RP11-160A10.2, the expression level in the recurrent group was significantly lower than that in the initial group, and the normal group was the highest; the difference was statistically significant (p < 0.05). Finally, we used the expression levels of AK124776 and RP11-160A10.2 in each group as the diagnostic indicators. According to the receiver operating curve (ROC), the accuracy of AK¬124776 and RP11-160A10.2 in the diagnosis of giant cell tumor of bone (area under the curve), the AUC was 0.865 and 0.877, respectively; the accuracy of predicting recurrence of giant cell tumor of bone was 0.832 and 0.841, respectively. CONCLUSIONS: The early detection of differential expression of lncRNAs in the serum of patients with giant cell tumor of bone is important for the diagnosis of disease and prediction of recurrence. The establishment of stable expression of lncRNAs and simple and easy detection methods are of great value for guiding clinical application.

Spectrum of histological features of Denosumab treated Giant Cell Tumor of Bone; potential pitfalls and diagnostic challenges for pathologists.

OBJECTIVES: Denosumab is Receptor Activator of Nuclear factor Kappa-B Ligand (RANKL) inhibitor which is being used in the treatment of locally advanced, recurrent and metastatic Giant Cell Tumor of Bone (GCTB). It causes reduction in monocyte recruitment and Osteoclast-Like Giant Cell (OLGC) formation which limits bone destruction. After Denosumab treatment, GCTB exhibit diverse morphological features which can pose diagnostic challenge. Our aim was to study the spectrum of histologic features seen in Denosumab treated GCTB which could be helpful in establishing correct diagnosis. METHODS: We retrieved and reviewed H&E stained microscopic glass slides of 38 GCTB cases who received Denosumab as neoadjuvant treatment. These cases were treated at different institutes and diagnosed at our institute between January 2017 and October 2019. Morphologic features such as presence of residual OLGC, appearances of mononuclear stromal and bony components were assessed along with other non-specific features. RESULTS: Patients' median age was 29 years. Male to female ratio was 1.53:1. Femur was the most commonly involved bone. Microscopically, peripheral shell of reactive bone was observed in all cases. In 20 (52.6%) cases, there was complete elimination of OLGC. Mononuclear stromal cells were predominantly bland spindle shaped and arranged in fascicular and storiform patterns. Focal atypia was noted in 3 cases. Bony component manifested as trabeculae of woven bone with osteoblastic rimming and immature trabeculae of unmineralized osteoid with haphazardly present osteoblasts. Spectrum of stromal changes included cystic spaces, foamy macrophages, inflammatory infiltrate, hemangiopericytoma-like (HPC-like) vessels, hyalinization, edematous areas and hemosiderin pigment. The tumors showed areas which resembled other bony and soft tissue lesions such non-ossifying fibroma, fibrous dysplasia, osteoblastoma, sclerosing epithelioid fibrosarcoma and osteosarcoma. CONCLUSION: Denosumab treatment induces a variety of changes in GCTB. Clinical history and knowledge of these features are necessary for excluding differential diagnoses and avoiding misdiagnosis.

Histone H3.3 mutation in giant cell tumor of bone: an update in pathology.

Giant cell tumor of bone (GCTB) is a locally aggressive bone tumor that frequently shows local recurrence and occasionally shows malignant transformation to high-grade sarcoma. Histologically, conventional GCTB is composed mainly of three types of cells: mononuclear neoplastic cells with an osteoblastic precursor phenotype, mononuclear histiocytic cells, and osteoclast-like multinucleated giant cells. These cells interact with each other via the RANKL-RANK axis and other mechanisms for tumor formation. The vast majority of GCTBs were recently revealed to harbor H3F3A p.G34W mutation, and a minor subset have H3F3A p.G34L, p.G34M, p.G34R, or p.G34V mutation. H3.3 G34W mutant-specific immunohistochemistry is a highly sensitive and specific surrogate marker for H3F3A p.G34W mutation in GCTB and thus useful for differential diagnoses of histological mimics. H3.3 mutant-specific immunohistochemistry has also contributed to the understanding of the bone-forming ability of neoplastic cells of GCTB and the remarkable new bone formation after treatment with denosumab, an inhibitor of RANKL. In primary and secondary malignant GCTBs, the H3F3A gene allele can be preserved or lost with malignant transformation.

[Expression of H3.3 G34W mutant-specific antibody in giant cell tumors of bone and its diagnostic value].

Objective: To investigate the expression of H3.3 G34W mutant-specific antibody in giant cell tumors of bone (GCTB), and its value in the diagnosis of GCTB. Methods: Immunohistochemical (IHC) EnVision method was used to detect the expression of H3.3 G34W mutant-specific antibody and p63 in 83 GCTBs, 18 aneurysmal bone cysts, 23 chondroblastomas and 28 osteosarcomas diagnosed at Nanjing Jinling Hospital from June 2001 to April 2019. Results: Among the 83 cases of GCTB, 69 cases (69/83, 83.1%) expressed H3.3 G34W. H3.3 G34W expression was found exclusively in the mononuclear cell population with strong and diffuse nuclear staining. H3.3 G34W was expressed in 55 of 57 (96.5%) cases of GCTB in long bones, but only 14 of 26 (53.8%) cases of non-long bone GCTB. All recurrent (9/9)/metastatic GCTB (2/2), post-denosumab GCTB (3/3), primary malignant GCTB (3/3) and secondary malignant GCTB (5/5) also expressed H3.3 G34W. H3.3 G34W was negative in all aneurysmal bone cysts and chondroblastomas. H3.3 G34W was positive in 3 of 28(10.7%) cases of osteosarcomas, and giant cell-rich osteosarcoma(GCRO) was the only histological subtype of osteosarcoma that expressed H3.3 G34W. p63 was expressed in 71.1%(59/83) of GCTB, while the positive rates of p63 in aneurysmal bone cysts,chondroblastomas and osteosarcomas were 3/18, 43.5% (10/23) and 21.4% (6/28) respectively. The sensitivity and specificity of H3.3 G34W mutant-specific antibody in the diagnosis of GCTB were 83.1% and 95.7%. Conclusions: H3.3 G34W mutant-specific antibody is a highly sensitive and specific marker for GCTB and helpful for the diagnosis of GCTB and its variants. The limitation of this antibody is that as a mall number of GCTB harbor G34 mutation other than G34W, and thus that cannot be detected. The incidental expression of H3.3 G34W mutant protein in osteosarcoma could be a potential diagnostic dilemma, and the results of H3.3 G34W IHC staining needs careful interpretation.

[Interpretation of 2020 NCCN Clinical Practice Guidelines in Oncology-Bone Cancer].

The specialty of bone cancer has developed rapidly in China in recent years, but because of the low incidence of these diseases and the unbalanced development of different regions, the malpractice problem of diagnosis and treatment is still outstanding.The NCCN clinical practice guide for bone cancer in the United States has been updated for several years and is now more mature and has been recognized worldwide.It can provide reference for medical professionals in related fields in China, it covers the most common bone tumors such as osteosarcoma, Ewing's sarcoma, chondrosarcoma, giant cell tumor of bone and chordoma.This article describes and interprets the core diagnostic and therapeutic contents of NCCN clinical practice guide for bone cancers.

Pseudomyogenic hemangioendothelioma of bone treated with denosumab: a case report.

BACKGROUND: Pseudomyogenic hemangioendothelioma (PMHE) is a rare endothelial neoplasm that involves the bones in only 14% of all cases. The optimal treatment strategy has not been established. We herein report a case of primary PMHE in which denosumab treatment showed activity in both imaging studies and the clinical outcome. CASE PRESENTATION: A 20-year-old woman presented with worsening pain in her left ankle. Imaging studies showed multifocal fluorodeoxyglucose (FDG)-avid [maximum standardized uptake value (SUVmax), 15.95] osteolytic lesions in the bones of her left lower extremity. While waiting for the definitive pathologic diagnosis of PMHE, denosumab, a human immunoglobulin G2 monoclonal antibody against RANKL, was initiated to treat progressive bone absorption after curettage of one of the lesions. Denosumab induced osteosclerosis around the lesions and pain relief and was discontinued 4 years after its initiation. Although all of the multifocal lesions remained, they all became less FDG-avid (SUVmax, 2.6), and the patient developed no signs of new lesions or distant metastasis. CONCLUSION: Denosumab plays a certain role in prevention of bone destruction by PMHE through suppression of osteoclast-like giant cells and would be an excellent treatment for bone absorption by PMHE of bone.

Stromal Cell-Derived CCL20 Promotes Tumor Progression and Osteolysis in Giant Cell Tumor of Bone.

BACKGROUND/AIMS: Giant cell tumor of bone (GCTB), one of the most common primary bone tumors, leads to extensive bone destruction. However, the mechanisms underlying GCTB progression remain elusive and prognostic factors and treatment targets are required. In the current study, we explored the function of the chemokine family member CCL20 in GCTB progression. METHODS: We explored the expression of CCL20 in stromal cells (GCTSCs) using microarray. Clinical analyses of the role of CCL20 in tumor progression were performed based on the patient cohort of our institution. The role of CCL20 in tumor proliferation was evaluated by MTS assay, migration ability was measured by a Transwell assay, and osteoclastogenesis was induced by CCL20 or GCTSC-conditioned medium. Quantitative PCR and western blot were used to measure the expression levels of mRNAs and proteins related to tumor progression. RESULTS: CCL20 was upregulated in GCTSCs and correlated with tumor progression and prognosis. CCL20 induced GCTSC proliferation and migration in an autocrine manner. In addition, CCL20 recruited mononuclear cells and induced osteoclastogenesis by overactivating the AKT and NF-κB signaling pathways. Antibody blockade of CCL20 abolished the exacerbated osteoclastogenesis. CONCLUSION: Taken together, our data indicate that GCTSC secretion of CCL20 acts as a key modulator in the pathological progression of GCTB. It can promote GCTSC proliferation and migration in an autocrine manner and can recruit bone marrow monocytes to the tumor microenvironment and enhance osteoclastogenesis in a paracrine manner. These findings strongly indicate the potential prognostic and therapeutic value of CCL20 in GCTB.

The identification of H3F3A mutation in giant cell tumour of the clivus and the histological diagnostic algorithm of other clival lesions permit the differential diagnosis in this location.

BACKGROUND: Giant Cell Tumour of Bone (GCT) is a locally aggressive primary bone tumour that usually occurs at the epiphyses of the long bones of the appendicular skeleton with a tendency to recurrence. Recurrent somatic H3F3A mutations have been described in 92% of GCT cases. GCTs involving the Clivus are extremely rare lesions and less than 15 cases are described in the literature. They represent a surgery challenge and are easily misdiagnosed. Our aim was to reveal if the genetic bases underlying Clival GCTs were the same of GCTs of long bones to improve the diagnosis and treatment. METHODS: The targeted somatic sequencing of GCT-related genes (H3F3A, H3F3B, IDH1, IDH2 and ZNF687) was performed on Clival GCT biopsies of two different cases. Histological analyses on the same tissues were used to detect the neoplastic population and its expression profile. RESULTS: Sanger sequencing revealed that both patients were positive for the p.Gly34Trp mutation in the H3F3A gene. Immunofluorescence assay using monoclonal antibody, specifically detecting the mutant H3.3, highlighted that the mutation only involved the mononuclear cell population and not the multinucleated giant cells. Moreover, immunohistochemistry assay showed that RANKL was highly expressed by the stromal cells within Clival GCT, mimicking what happens in GCT of the long bones. In addition, systematic literature review allowed us to generate a histology-based diagnostic algorithm of the most common clival lesions. CONCLUSIONS: We conclude that the Clival GCT is genetically defined by somatic mutation in the H3F3A gene, linking it to the GCT of long bones. The similarity with GCTs of long bones let us to hypothesize the utility of Denosumab therapy (already effective for GCTs) in these surgically challenging cases. Moreover, H3F3A genetic screening can be combined to the histological analysis to differentiate GCTs from morphologically similar giant cell-rich sarcomas, while the histological diagnostic algorithm could help the differential diagnosis of other clival lesions.

Cystic bone tumors of the foot and ankle.

Bone tumors are relatively rare in the foot and ankle region. Many of them present as cystic lesions on plain films. Due to the relative rarity of these lesions and the complex anatomy of the foot and ankle region, identification of such lesions is often delayed or they get misdiagnosed and mismanaged. This review discusses the most common cystic tumors of the foot and ankle including their radiographic features and principles of management.

[Benign and malignant giant-cell rich lesions of bone: Pathological diagnosis with special emphasis on recent immunohistochemistry and molecular techniques]. / Diagnostic des lésions osseuses riches en cellules géantes : démarche diagnostique et intérêt des nouvelles techniques complémentaires immuno-histochimiques et moléculaires.

The infiltration by numerous osteoclastic giant cells is a frequent finding in bone tumors and pseudo-tumors. Pathologists must integrate clinical and radiological data to achieve a correct diagnosis in bone pathology. Benign giant-cell rich lesions of bone encompass giant cell tumor of bone, aneurysmal bone cyst, chondroblastoma, brown tumor and fibrous cortical defect/non-ossifying fibroma. Amongst malignant neoplasms, variants of conventional osteosarcoma, undifferentiated pleomorphic sarcoma, leiomyosarcoma and bone metastasis must be discussed. Recently, new diagnostic markers, antibodies for immuno-histochemistry and genetic markers, have been developed and are helpful to diagnose such lesions.