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

Malignant Giant Cell Tumor of Bone: A Clinicopathologic Series of 28 Cases Highlighting Genetic Differences Compared With Conventional, Atypical, and Metastasizing Conventional Tumors

Giant cell tumors of bone are locally aggressive, frequently harbor H3F3A p.G34W mutations, and rarely undergo malignant transformation. The pathogenesis of malignant transformation remains incompletely characterized. Herein, we present 28 malignant giant cell tumors of bone from 14 males and 14 females, aged 16 to 65 (median 39) years. Primary sites included long bones (n=20), pelvis (n=3), vertebrae (n=2), and rarely rib, phalanx, and cuneiform (n=1 each). Sixteen (62%) of 26 tumors with available history represented malignant transformation or recurrence of conventional giant cell tumors of bone, at intervals of 1.3 to 35 (median 7.3) years before malignant transformation. Eight of 15 patients with available treatment history received denosumab before a diagnosis of malignancy. Ten (38%) of 26 tumors with available history likely arose de novo, including 7 with conventional areas and 3 H3F3A -mutant sarcomas lacking conventional giant cell tumor of bone. Of 28 malignant giant cell tumors of bone, 18 (64%) and 10 (36%) harbored osteoblastic and chondroblastic elements, respectively. Among 23 tumors with available genetic testing or surrogate immunohistochemistry, 17 (74%) were p.G34W-mutant, whereas other tumors carried H3F3A p.G34L (n=2), p.G34V (n=2), and p.G34R (n=1) alterations; 1 tumor harbored H3F3B p.K116E and p.R117S in cis. Seven (70%) of 10 malignant giant cell tumors of bone showed complex copy number alterations by single nucleotide polymorphism (SNP) array, DNA next-generation sequencing (NGS), and/or karyotype analysis. In contrast, complex chromosomal alterations were lacking in 32 conventional giant cell tumors of bone tested (24 by karyotype, 7 by SNP array, 1 by DNA NGS), 3 atypical giant cell tumors of bone with isolated marked nuclear atypia (2 by karyotype, 1 by SNP array) and 3 metastasizing conventional giant cell tumors of bone (2 by DNA NGS, 1 by karyotype). Clinical follow-up was available for 20 patients (71%), and one additional patient had metastases at presentation. Overall, 14 of 21 patients (67%) developed metastases, and 10 of 20 patients with follow-up (50%) died of disease at 2 months to 9.6 years (median 7 mo). Most patients were treated with chemotherapy; 1 patient (PD-L1 TPS >95%) was treated with pembrolizumab, with complete clinical response of metastatic disease at 2.5 years. In conclusion, malignant giant cell tumors of bone typically arise from long bones, harbor osteosarcomatous and/or chondrosarcomatous differentiation, and show significant risk for distant metastasis and demise. Our data suggest that copy number analysis may be useful in distinguishing malignant giant cell tumors of bone from their conventional, atypical, and metastasizing conventional counterparts.

Molecular pathological insights into tumorigenesis and progression of giant cell tumor of bone

Giant cell tumor of bone (GCTB) is a primary bone tumor that typically exhibits benign histological appearance and clinical behavior in most cases, with local aggressiveness and rare metastasis. It predominantly affects individuals in the young adult age group. It is characterized by the presence of multinucleated osteoclastic giant cells and a stromal population of neoplastic cells. A key hallmark for GCTB pathogenesis is the G34W genetic mutation in the histone H3.3 gene, which is restricted to the population of cancerous stromal cells and is absent in osteoclasts and their progenitor cells. This review presents a comprehensive overview of the pathology of GCTB, including its histopathological characteristics, cytological features, histopathological variants, and their clinical relevance. We also discuss recent insights into genetic alterations in relation to the molecular pathways implicated in GCTB. A summary of the current understanding of GCTB pathology will update the knowledge base to guide the diagnosis and management of this unique bone tumor.

Giant Cell-Rich Tumors of the Skeleton

The accurate diagnosis of giant cell-rich tumors of bone is challenging, especially in limited tissue samples. This diverse group of neoplasms have similar and often ambiguous clinical presentations, radiologic features, and morphologic characteristics. During the last decade, the discovery of pathogenic recurrent genetic alterations has allowed the development of immunohistochemical surrogate markers and FISH assays that can help differentiate the entities of this broad group from one another. The correct diagnosis of these neoplasms is essential in the management of the affected patients.

Pediatric Mesenchymal Tumors

Vascular, fibrous/myofibroblastic, and myogenic tumors account for the majority of mesenchymal tumors in children. These tumors often show significant overlap in morphology and immunophenotype posing diagnostic difficulties and, thus, their classification remains challenging. Recent advances in immunohistochemistry have proved helpful in identifying a specific line of differentiation in some tumors, but other tumors remain difficult to classify. Molecular investigations have provided an existing tool to better understand the pathogenesis of some of these tumors and, in some cases like the EWING family of tumors, expanded the classification resulting in the emergence of previously unknown tumors. Some of these tumors are currently diagnosed according to their underlying molecular abnormality, such as CIC -rearranged sarcoma, BCOR -rearranged sarcoma, etc. This review focuses on the common mesenchymal neoplasms of the pediatric population with emphasis on the salient histologic features, immunoprofile, and molecular characteristics. For practical purposes, the latter are summarized in Supplemental Table 1, Supplemental Digital Content 1, http://links.lww.com/PAP/A46 .

Giant cell tumor of distal radius: En bloc resection with allograft reconstruction: A case report

Key Clinical Message

Giant cell tumor of bone (GCT) is a rare neoplasm which often presents as a lytic lesion in the epiphyseal region of long bones and which are usually accompanied by pain, swelling, and restricted movement.

Abstract

Giant cell tumor of bone (GCT) is a rare neoplasm that affects individuals in their third and fourth decades of life. Clinically, it often presents as a lytic lesion in the epiphyseal region of bones, notably the distal femur and proximal tibia. Radiologically, GCT appears as a distinct lytic lesion in the epiphyseal region. Histopathologically, GCTs are composed of mononuclear cells, macrophages, and multinuclear giant cells, indicative of osteoclastogenic stromal tumors. A 37-year-old man presented with left wrist pain, swelling, and restricted movement persisting for a year, worsening over the last 7 months. Radiographic assessments revealed a distal radius bone mass involving the radiocarpal joint. Biopsy confirmed a GCT with extension into peripheral muscle. PET/CT scan showed localized pathology without metastasis. Histopathologically, GCT exhibited multinucleated giant cells, spindle cells, and aneurysmal bone cyst-like regions with coagulation necrosis. Surgical resection involved en-bloc removal and reconstruction with a non-vascularized radius bone graft. Postoperatively, the patient showed no complications at the one-year follow-up, suggesting successful intervention.

Current Concepts in the Treatment of Giant Cell Tumor of Bone: An Update

Curettage is recommended for the treatment of Campanacci stages 1-2 giant cell tumor of bone (GCTB) in the extremities, pelvis, sacrum, and spine, without preoperative denosumab treatment. In the distal femur, bone chips and plate fixation are utilized to reduce damage to the subchondral bone and prevent pathological fracture, respectively. For local recurrence, re-curettage may be utilized when feasible. En bloc resection is an option for very aggressive Campanacci stage 3 GCTB in the extremities, pelvis, sacrum, and spine, combined with 1-3 doses of preoperative denosumab treatment. Denosumab monotherapy once every 3 months is currently the standard strategy for inoperable patients and those with metastatic GCTB. However, in case of tumor growth, a possible malignant transformation should be considered. Zoledronic acid appears to be as effective as denosumab; nevertheless, it is a more cost-effective option. Therefore, zoledronic acid may be an alternative treatment option, particularly in developing countries. Surgery is the mainstay treatment for malignant GCTB.

Giant Cell Tumor of Mandible : A Case Report

Giant cell tumor is locally aggressive primary benign neoplasm of bone with tendency of frequent recurrence, metastasis and malignant transformation. Because of the rarity of the disease involving mandible, no definite treatment guideline is established. Surgical treatment is the treatment of choice for giant cell tumor. Due to its proximity to vital structures including skull base, the recurrent disease associated with less invasive procedure could be difficult to manage while more invasive procedure will result in higher morbidity and complex reconstruction. Medical management with denosumab or zoledronic acid has been advocated in surgically unresectable disease. We present a rare case of giant cell tumor of mandible. Patient was a 33 years old lady who presented with gradually progressive painful swelling in chin. After exclusion of distant metastasis by F-18 FDG PET scan, she underwent en-bloc resection of the tumor with free fibula flap reconstruction. During 6 months of follow up visit patient had no recurrence.

Clinical genomic profiling of malignant giant cell tumor of bone: A retrospective analysis using a real‑world database

Malignant giant cell tumor of bone (GCTB) is identified by the presence of multinucleated giant cells, with an aggressive behavior and a high risk of metastasis, which has not been genetically characterized in detail. H3 histone family member 3A (H3F3A) gene mutations are highly recurrent and specific in GCTB. The present study analyzed the clinical information and genomic sequencing data of eight cases of malignant GCTB (out of 384 bone sarcoma samples) using an anonymized genomic database. There were 5 males and 3 females among the cases, with a median age of 33 years at the time of the initial diagnosis. H3F3A G34W and G34L mutations were detected in 3 patients and 1 patient, respectively. In 75% of cases without H3F3A mutation, mitogen-activated protein kinase (MAPK) signaling pathway gene alterations were found (KRAS single nucleotide variant, KRAS amplification, nuclear respiratory factor 1-BRAF fusion). Moreover, the collagen type I alpha 2 chain-ALK fusion was detected in remaining one case. The most frequent gene alterations were related to cell cycle regulators, including TP53, RB1, cyclin-dependent kinase inhibitor 2A/B and cyclin E1 (75%, 6 of 8 cases). On the whole, the present study discovered recurrent MAPK signaling gene alterations or other gene alterations in cases of malignant GCTB. Of note, two fusion genes should be carefully validated following the pathology re-review by sarcoma pathologists. These two fusion genes may be detected in resembling tumors, which contain giant cells, apart from malignant GCTB. The real-world data used herein provide a unique perspective on genomic alterations in clinicopathologically diagnosed malignant GCTB.

Genetic characterization of a novel organoid from human malignant giant-cell tumor

Malignant giant-cell tumors are extremely rare bone sarcomas that transform from conventional giant-cell tumors during long periods of treatment. Owing to their rarity, no further analysis of their molecular pathogenesis exists, and thus, no standard treatment has been established. Recently, organoid culture methods have been highlighted for recapturing the tumor microenvironment, and we have applied the culture methods and succeeded in establishing patient-derived organoids (PDO) of rare sarcomas. This study aimed to investigate the genomic characteristics of our established novel organoids from human malignant giant-cell tumors. At our institute, we treated a patient with malignant giant-cell tumor. The remaining sarcoma specimens after surgical resection were cultured according to the air-liquid interface organoid-culture method. Organoids were xenografted into NOD-scid IL2Rgnull mice. The developed tumors were histologically and genomically analyzed to compare their characteristics with those of the original tumors. Genetic changes over time throughout treatment were analyzed, and the genomic status of the established organoid was confirmed. Organoids from malignant giant-cell tumors could be serially maintained using air-liquid interface organoid-culture methods. The tumors developed in xenografted NOD-scid IL2Rgnull mice. After several repetitions of the process, a patient-derived organoid line from the malignant giant-cell tumor was established. Immunohistochemical analyses and next-generation sequencing revealed that the established organoids lacked the H3-3A G34W mutation. The xenografted organoids of the malignant giant-cell tumor had phenotypes histologically and genetically similar to those of the original tumor. The established organoids were confirmed to be derived from human malignant giant-cell tumors. In summary, the present study demonstrated a novel organoid model of a malignant giant-cell tumor that was genetically confirmed to be a malignant transformed tumor. Our organoid model could be used to elucidate the molecular pathogenesis of a malignant giant-cell tumor and develop novel treatment modalities.

In situ sequence-specific visualization of single methylated cytosine on tissue sections using ICON probe and rolling-circle amplification

Since epigenetic modifications differ from cell to cell, detecting the DNA methylation status of individual cells is requisite. Therefore, it is important to conduct "morphology-based epigenetics research", in which the sequence-specific DNA methylation status is observed while maintaining tissue architecture. Here we demonstrate a novel histochemical technique that efficiently shows the presence of a single methylated cytosine in a sequence-dependent manner by applying ICON (interstrand complexation with osmium for nucleic acids) probes. By optimizing the concentration and duration of potassium osmate treatment, ICON probes selectively hybridize to methylated cytosine on tissue sections. Since the elongation process by rolling-circle amplification through the padlock probe and synchronous amplification by the hyperbranching reaction at a constant temperature efficiently amplifies the reaction, it is possible to specifically detect the presence of a single methylated cytosine. Since the ICON probe is cross-linked to the nuclear or mitochondrial DNA of the target cell, subsequent elongation and multiplication reactions proceed like a tree growing in soil with its roots firmly planted, thus facilitating the demonstration of methylated cytosine in situ. Using this novel ICON-mediated histochemical method, detection of the methylation of DNA in the regulatory region of the RANK gene in cultured cells and of mitochondrial DNA in paraffin sections of mouse cerebellar tissue was achievable. This combined ICON and rolling-circle amplification method is the first that shows evidence of the presence of a single methylated cytosine in a sequence-specific manner in paraffin sections, and is foreseen as applicable to a wide range of epigenetic studies.

Loss of H3K27 trimethylation in a distinct group of de-differentiated chordoma of the skull base

De-differentiated chordoma is defined as a high-grade sarcoma lacking notochordal differentiation, which arises in association with conventional chordoma. The mechanism underlying de-differentiation remains unclear. We immunohistochemically investigated trimethylation at lysine 27 of histone 3 (H3K27me3) in nine de-differentiated chordomas. The tumours occurred at the skull base (n = 5) or the sacrum (n = 4) in four men and five women with a median age of 50 years. De-differentiation occurred de novo in four cases and at recurrence/metastasis in five cases. Five tumours retained H3K27me3, whereas four showed complete loss of H3K27me3 only in the de-differentiated component, while the conventional chordoma component retained H3K27me3. All the H3K27me3-negative tumours showed co-loss of dimethylation at H3K27 (H3K27me2), consistent with inactivation of polycomb repressive complex 2. Two genetically analysed H3K27me3-negative tumours harboured EED homozygous deletions. All four H3K27me3-negative de-differentiated chordomas affected the skull base of young or middle-aged women. Unlike dense proliferation of highly pleomorphic spindle or epithelioid cells in the H3K27me3-positive de-differentiated chordomas, all H3K27me3-negative tumours displayed swirling fascicles of relatively uniform spindle cells with alternating cellularity and perivascular accentuation, resembling malignant peripheral nerve sheath tumour (MPNST). Rhabdomyoblastic differentiation was present in one H3K27me3-negative tumour. We identified a novel group of de-differentiated chordomas in the skull base that lost H3K27me3/me2 only in the de-differentiated component, which was associated with EED homozygous deletion and MPNST-like histology. Our data suggest a distinct 'polycomb-type' de-differentiation pathway in chordoma, similar to a recently described de-differentiated chondrosarcoma with H3K27me3 loss.

Nanomaterial-assisted CRISPR gene-engineering - A hallmark for triple-negative breast cancer therapeutics advancement

Triple-negative breast cancer (TNBC) is the most violent class of tumor and accounts for 20-24% of total breast carcinoma, in which frequently rare mutation occurs in high frequency. The poor prognosis, recurrence, and metastasis in the brain, heart, liver and lungs decline the lifespan of patients by about 21 months, emphasizing the need for advanced treatment. Recently, the adaptive immunity mechanism of archaea and bacteria, called clustered regularly interspaced short palindromic repeats (CRISPR) combined with nanotechnology, has been utilized as a potent gene manipulating tool with an extensive clinical application in cancer genomics due to its easeful usage and cost-effectiveness. However, CRISPR/Cas are arguably the efficient technology that can be made efficient via organic material-assisted approaches. Despite the efficacy of the CRISPR/Cas@nano complex, problems regarding successful delivery, biodegradability, and toxicity remain to render its medical implications. Therefore, this review is different in focus from past reviews by (i) detailing all possible genetic mechanisms of TNBC occurrence; (ii) available treatments and gene therapies for TNBC; (iii) overview of the delivery system and utilization of CRISPR-nano complex in TNBC, and (iv) recent advances and related toxicity of CRISPR-nano complex towards clinical trials for TNBC.

Clinicopathological and histological analysis of secondary malignant giant cell tumors of bone without radiotherapy

Giant cell tumor of bone (GCTB) is an intermediate bone tumor that rarely undergoes malignant transformation. Secondary malignant GCTB (SMGCTB) is defined as a lesion in which high-grade sarcoma occurs at the site of previously treated GCTB. The present study retrospectively reviewed the medical records of patients with GCTB treated at Okayama University Hospital between April 1986 and April 2020. The clinicopathological and histological features of patients with SMGCTB without prior radiotherapy were investigated. A total of three patients (4%) with SMGCTB were detected, and the tumor sites were the distal ulna, distal femur and sacrum. Two of the patients had been treated with curettage and bone graft, and one had been treated with denosumab. In all cases, the lesions were made up of two components, the conventional GCTB component and the malignant component. The Ki67 labeling index was higher in the malignant components of SMGCTB and metastatic lesions compared with that in primary and recurrent conventional GCTB, or the conventional GCTB component of SMGCTB. Moreover, p53 expression was higher in these same components in patients who underwent curettage and bone grafting; however, there was no difference in the patient that received denosumab treatment. In this patient, clinical cancer genomic profiling revealed loss of CDKN2A, CDKN2B and MTAP expression. All three patients developed distant metastasis. The patients with SMGCTB in the ulna and femur died 13 and 54 months after detection of malignant transformation, respectively. The patient with SMGCTB in the sacrum received carbon-ion radiotherapy to the sacrum and pazopanib; the treatment was effective and the patient was alive at the last follow-up 3 years later. In conclusion, p53 may be associated with malignant transformation in GCTB. Future studies should investigate the association of between denosumab treatment and malignant transformation, as well as molecular targeted therapy to improve the clinical outcomes of SMGCTB.

A Multiparametric Method Based on Clinical and CT-Based Radiomics to Predict the Expression of p53 and VEGF in Patients With Spinal Giant Cell Tumor of Bone

Purpose

This project aimed to assess the significance of vascular endothelial growth factor (VEGF) and p53 for predicting progression-free survival (PFS) in patients with spinal giant cell tumor of bone (GCTB) and to construct models for predicting these two biomarkers based on clinical and computer tomography (CT) radiomics to identify high-risk patients for improving treatment.

Material and Methods

A retrospective study was performed from April 2009 to January 2019. A total of 80 patients with spinal GCTB who underwent surgery in our institution were identified. VEGF and p53 expression and clinical and general imaging information were collected. Multivariate Cox regression models were used to verify the prognostic factors. The radiomics features were extracted from the regions of interest (ROIs) in preoperative CT, and then important features were selected by the SVM to build classification models, evaluated by 10-fold crossvalidation. The clinical variables were processed using the same method to build a conventional model for comparison.

Results

The immunohistochemistry of 80 patients was obtained: 49 with high-VEGF and 31 with low-VEGF, 68 with wild-type p53, and 12 with mutant p53. p53 and VEGF were independent prognostic factors affecting PFS found in multivariate Cox regression analysis. For VEGF, the Spinal Instability Neoplastic Score (SINS) was greater in the high than low groups, p < 0.001. For p53, SINS (p = 0.030) and Enneking stage (p = 0.017) were higher in mutant than wild-type groups. The VEGF radiomics model built using 3 features achieved an area under the curve (AUC) of 0.88, and the p53 radiomics model built using 4 features had an AUC of 0.79. The conventional model built using SINS, and the Enneking stage had a slightly lower AUC of 0.81 for VEGF and 0.72 for p53.

Conclusion

p53 and VEGF are associated with prognosis in patients with spinal GCTB, and the radiomics analysis based on preoperative CT provides a feasible method for the evaluation of these two biomarkers, which may aid in choosing better management strategies.