Histologic Spectrum of Giant Cell Tumor (GCT) of Bone in Patients 18 Years of Age and Below: A Study of 63 Patients

Histones and their practical application in bone tumors: Do I always need them?

Historically, the diagnosis of giant cell-rich neoplasms arising in bone has been challenging owing to overlapping clinical and radiographic findings resulting in the difficult separation of several neoplasms, particularly when biopsy material is limited. However, with the discovery of the driver histone mutations in giant cell tumor of bone (GCTB) and chondroblastoma, as well as USP6 rearrangements in aneurysmal bone cyst, pathologists now have objective ancillary tools to aid in the separation of several histologically similar giant cell-rich neoplasms. Furthermore, the recognition of histone mutations has allowed pathologists to revisit several entities, such as "malignant chondroblastoma," and furthered our understanding of phenomena such as "aneurysmal bone cyst-like change," formerly recognized as "secondary aneurysmal bone cyst." Herein, the evolution of testing for histone mutations in bone tumors is considered; the sensitivity and specificity of the histone antibodies is reviewed; and a practical guide for the use of these ancillary tests is offered.

Keratin-Positive Giant Cell-Rich Tumor of Bone Harboring an HMGA2::NCOR2 Fusion: Two Cases, Including a Patient With Metastatic Disease, and Review of the Literature

Giant cell-rich lesions of bone represent a heterogeneous group of entities which classically include giant cell tumor of bone, aneurysmal bone cyst, nonossifying fibroma, and Brown tumor of hyperparathyroidism. A recently described subset of giant cell-rich tumors involving bone and soft tissue has been characterized by recurrent HMGA2::NCOR2 fusions and keratin expression. The overlapping clinical, radiographic, and morphological features of these giant cell-rich lesions provide a unique diagnostic challenge, particularly on biopsy. We present 2 additional cases of keratin-positive giant cell-rich tumor of bone with HMGA2::NCOR2 fusions, including 1 patient who developed metastatic disease.

Surgical Treatments and Long-Term Outcomes for Pediatric Patients With Lumbar Spinal Tumors

STUDY DESIGN

Retrospective case‒control study.

OBJECTIVES

This study aimed to report the effects of surgical intervention on spinal stability recovery and to assess the long-term outcomes of children and adolescents with lumbar tumors.

METHODS

From January 2016 to June 2021, 42 pediatric patients with lumbar tumors were selected and separated into different groups based on the surgical method used (total en bloc resection (TER) group, n = 21; piecemeal resection (PR) group, n = 21; titanium mesh (TM) group n = 23; artificial vertebrae (AV) group n = 19). The clinicopathological characteristics, treatments and related outcomes were described in detail and compared between groups, with P value ≤.05 indicating statistically significant differences.

RESULTS

The average follow-up duration was 24.89 months, and the mean age was 14.89 ± 2.41 years. There were no significant differences in the mean operation time, average blood loss, complication rate, or length of hospital stay between the groups. The ODI, VAS and JOA scores at the final follow-up (FF) were elevated after surgery in all groups. The FF local angular drift (LOD) and lumbar angular drift (LUD) were greater in the TM group than in the AV group (P = .03, P = .001).

CONCLUSIONS

After surgery, pediatric patients with lumbar tumors can obtain satisfactory spinal stability, effective relief of pain symptoms and substantial improvements in neurological function. There was no significant difference in the invasiveness, safety or timeliness between the 2 surgical methods, so TER is recommended due to its low postoperative recurrence rate and good local control. Spinal fusion in the AV group resulted in better spinal stability.

The efficacy and safety of short-course neoadjuvant denosumab for en bloc spondylectomy in spinal giant cell tumor of bone: a preliminary report

PURPOSE

This study aimed to investigate whether short course of neoadjuvant denosumab treatment for spinal GCTB could (1) Induce radiological and histological response? (2) Facilitate en bloc resection? (3) Achieve satisfactory oncological and functional outcomes?

METHODS

The clinical information of ten consecutive patients between 2018 and 2022 with spinal GCTB treated with short course of neoadjuvant denosumab (≤ 5 doses) and en bloc spondylectomy was retrospectively reviewed. The radiological and histological response, operative data, oncological and functional outcomes were analyzed.

RESULTS

The mean doses of neoadjuvant denosumab were 4.2 (range 3-5 doses). After neoadjuvant denosumab, there were 9 cases showing new ossification and 5 cases with reappearance of cortical integrity. The values of Hounsfield units (HU) of the soft tissue component were increased by > 50% in 7 cases. The signal intensity (SI) ratios of tumor/muscle in T2WI of plain MRI were decreased by > 10% in 60% of the cases. Shrinkage of soft tissue mass by > 10% was observed in 4 cases. The mean duration of operation was 575 ± 174 min, and the mean estimated blood loss (EBL) was 2790 ± 1934 ml. No obvious adhesion to dura mater or major vessels was encounter intraoperatively. There is no tumor collapse or breakage during surgery. Multinucleated giant cells were decreased in 6 cases (60%) with the remaining 4 cases showing absence of multinucleated giant cells. Mononuclear stromal cells existed in most of the cases (8 cases, 80%). New bone formation was noticed in 8 cases (80%). No patient had a worsening of neurologic function after surgery. No tumor recurrence was noticed within the mean follow-up of 24 ± 20 months.

CONCLUSION

Short-term neoadjuvant denosumab could yield radiological and histological responses and might facilitate en bloc spondylectomy by hardening the tumor and causing less adhesion to segmental vessels, major vessels and nerve roots, which was beneficial to achieve the optimal oncological and functional outcomes.

Targeting epigenetic aberrations of sarcoma in CRISPR era

Sarcomas are rare malignancies that exhibit diverse biological, genetic, morphological, and clinical characteristics. Genetic alterations, such as gene fusions, mutations in transcriptional machinery components, histones, and DNA methylation regulatory molecules, play an essential role in sarcomagenesis. These mutations induce and/or cooperate with specific epigenetic aberrations required for the growth and maintenance of sarcomas. Appropriate mouse models have been developed to clarify the significance of genetic and epigenetic interactions in sarcomas. Studies using the mouse models for human sarcomas have demonstrated major advances in our understanding the developmental processes as well as tumor microenvironment of sarcomas. Recent technological progresses in epigenome editing will not only improve the studies using animal models but also provide a direct clue for epigenetic therapies. In this manuscript, we review important epigenetic aberrations in sarcomas and their representative mouse models, current methods of epigenetic editing using CRISPR/dCas9 systems, and potential applications in sarcoma studies and therapeutics.

Diagnostic value of H3F3A mutation and clinicopathological features of giant cell tumours in non-long bones

Aims

A histone H3F3A (H3.3) mutation involving a substitution in H3.3 G34 recently has been reported in GCTB within the frequency range (from 69 % to 96 %) and is a helpful diagnostic indicator of GCTB. However, the relationship between H3F3A mutations and the clinicopathological feature of GCTB involving non-long bones (irregular bones and small bones) is unclear.

Methods and results

H3F3A mutations were observed in a cohort of specimens (230 samples of GCTB) using immunohistochemistry and Sanger sequencing. The relationship between H3F3A mutations and the clinicopathological characteristics of patients with GCTB occurring in the non-long bones of the appendicular skeleton was investigated. No significant difference between H3F3A mutations in GCTB arising in non-long bones and the classic sites was found (P = 0.483). GCTB in non-long bones occurred more common in female (31/49, 63.3 %) than in male patients (P = 0.016). GCTB with H3.3 G34L/V/R mutation occurred more often in younger patients compared with those with H3.3 G34W mutation (P = 0.009). The majority of GCTB with soft tissue extension developed in irregular bones but not in small bones (P = 0.061). The H3.3 G34L/V/R mutations rate (7/45) in the non-long bones was significantly higher than that in long bones. The recurrence rate of the GCTB in long bones and non-long bones was 23.3 % (45/193) including 43 cases with local recurrene and 2 cases with lung metastasis. No recurrence occurred in cases with G34V/L/R mutations.

Conclusions

H3F3A was an effective diagnostic marker for GCTB of the non-long bones. The younger patients with GCTB of the non-long bones harboured H3.3 G34L/V/R mutations and may had a female preference and rarely recurrent.

Imaging features, staging system, and surgical management of giant cell lesions of the temporal bone

BACKGROUND

Giant cell tumors (GCTs) and giant cell granulomas (GCGs) are giant cell-rich lesions that occur extremely rarely in the temporal bone and have similar clinical presentations.

OBJECTIVES

We aimed to analyze the clinical features and introduce our staging system and surgical treatment.

METHODS

Forty-six patients pathologically diagnosed with a giant cell lesion involving the temporal bone between October 2001 and October 2020 were reviewed retrospectively. The clinical characteristics, surgical approaches, and risk factors for recurrence were analyzed.

RESULTS

GCTs and GCGs presented as masses centered on the temporomandibular joint with similar imaging features, including a thin, calcified shell and central scattered calcifications on a computed tomography scan. Differences were detected on magnetic resonance imaging in 29.6% (4/14) of GCG and 50% (16/32) of GCT cases; the remaining cases were not distinguishable. Based on our staging system and surgical strategy, 31.8% (7/22) of GCT and 10% (1/10) of GCG cases experienced recurrence, which compares to recurrence rates of 60% in GCT cases and 20% in GCG cases in previous studies.

CONCLUSIONS

Specific clinical and preoperative imaging features help to make a diagnosis of temporal giant cell-rich lesions. Our staging system and surgical strategy could help surgeons tailor the surgical strategy.

Ultra-Short Course of Neo-Adjuvant Denosumab for Nerve-Sparing Surgery for Giant Cell Tumor of Bone in Sacrum

STUDY DEIGN

This was a retrospective study about sacral giant cell tumor of bone (GCTB).

OBJECTIVE

This study aimed to investigate whether ultra-short course of neo-adjuvant denosumab treatment for sacral GCTB could (1) induce radiological and histological response? (2) Facilitate nerve-sparing surgery? (3) Achieve satisfactory oncological and functional outcomes?

SUMMARY OF BACKGROUND DATA

Previous reports on long course of neo-adjuvant denosumab treatment for GCTB showed significant tumor response and a relatively high recurrent rate after curettage.

METHODS

Sixty-six patients with sacral GCTB treated with neoadjuvant denosumab and nerve-sparing surgery were categorized into ultra-short course group (≤3 doses and operation within D21 since 1st dose, 41 patients) or conventional group (>3 doses or operation after D21 since 1st dose, 25 patients). The radiological and histological response, operative data, oncological and functional outcomes were compared.

RESULTS

The ultra-short course group demonstrated fewer doses of neo-adjuvant denosumab (mean: 2.1 vs. 4.8, P  < 0.001) and shorter time to surgery (12.2 days vs. 72.3 days, P < 0.001). Similar patterns of radiological and histological response were observed in the two groups with less fibrosis and ossification in the ultra-short course group. The operative duration (199.9 min vs. 187.8 min, P = 0.364) and estimated blood loss (1552.4 mL vs. 1474.0 mL, P = 0.740) were comparable. Most (94.8%) of the patients received adjuvant denosumab. After a mean follow-up of 29.4 months, three cases (8.8%) and five cases (20.8%) showed local recurrence in each group (P = 0.255). The estimated recurrence-free survival (56.2 vs. 51.2 months, P = 0.210) and the functional status [Motor-Urination-Defecation scores: 25.9 vs. 25.7, P = 0.762] did not differ between the two groups.

CONCLUSION

Ultra-short course of neo-adjuvant denosumab for sacral GCTB could elicit radiological and histological responses as conventional course did. The less degree of fibrosis and ossification might facilitate nerve-sparing surgery and help to achieve satisfactory local control and functional status.Level of Evidence: 4.

Giant Cell Tumors of Bone in Patients Aged 18 Years Old or Younger: Imaging Features and Tumor Characteristics

Objective

The majority of giant cell tumors of bone (GCTB) occur in adult patients, especially between the ages of 20 and 40. This study aims to investigate the imaging features of GCTBs in pediatric patients and compare their characteristics with adult cases.

Methods

Fifty-seven cases of patients aged 18 years old or younger were retrospectively analyzed, accounting for 12.8% of GCTBs in the First Affiliated Hospital of Zhengzhou University from 2001 to 2019. One hundred twenty-six adult patients (19 years of age and older) with GCTB occurring in long tubular bones were also included in this study. The following clinical information was identified from the medical records: age, sex, and follow-up data. Imaging features were reviewed by two musculoskeletal radiologists. Patient characteristics and imaging features between the two groups were compared.

Results

A total of 57 patients (32 females, 25 males) were included in the study. The patients’ ages ranged from 9 to 18 (median = 17 y). The majority of tumors occurred in tubular bones (n = 38, 66.7%) and the pelvis (n = 8, 14.0%). Imaging features were identified in GCTB cases occurring in the long tubular bones. Compared with adult GCTB patients, pediatric GCTB patients had a larger superior–inferior (SI) diameter (P = 0.005) and smaller left-to-right diameter/SI diameter ratio (P = 0.001). Epiphyseal involvement was relatively less common in pediatric patients with GCTBs than in adult patients (P = 0.009). The median age of patients without epiphyseal involvement was lower than the median age of patients with epiphyseal involvement (11 vs 17 y).

Conclusion

GCTB in the pediatric age group is rare. This study has found that, in pediatric patients with GCTBs, the epiphysis is relatively less involved, and the tumor is more likely to grow longitudinally. These findings are helpful in the diagnosis of GCTBs in the pediatric population.

Gene of the month: H3F3A and H3F3B

H3F3A and H3F3B genes are located at 1q42.12 and 17q25.1, respectively, and encode identical H3.3 core histone proteins which form part of the histone hetero-octamer complex. Histones function by packaging DNA into small units, the nucleosome, and are highly susceptible to epigenetic post-translational modification. H3 K27 mutations have been shown to inhibit the polycomb repressive complex 2, which is normally involved in epigenetic gene silencing. Mutations in H3F3A and H3F3B are increasingly recognised in a variety of solid tumours. Point mutations in H3F3A have been described in giant cell tumour of bone and paediatric-type diffuse high-grade gliomas. Mutations in H3F3B have been described in chondroblastoma. Loss of trimethylation of H3 K27 is characteristic of most sporadic and radiation-associated malignant peripheral nerve sheath tumours. Immunohistochemistry with a variety of novel antibodies directed against specific mutations, as well as loss of H3K27me3 staining, may be useful in specific settings and in diagnostically challenging cases.

Giant Cell-Rich Tumors of Bone

The term giant cell-rich tumors of bone refers to a shared morphologic pattern in a group of different osseous lesions, that is, the abundance of osteoclastlike giant cells. Fitting with a broad spectrum of clinical presentations and biological behavior, the recent detection of characteristic molecular alterations in giant cell tumor of bone (H3-3), nonossifying fibroma (KRAS, FGFR1), giant cell granuloma of the jaws (KRAS, FGFR1, TRPV4), and aneurysmal bone cyst (USP6) have contributed significantly to the biological understanding of these morphologically related but clinically distinct lesions and their systematic classification, highlighting differences and pathogenic relationships.

Giant cell tumor of bone - Analysis of 213 cases involving extra-craniofacial bones

We elucidated clinicopathological characteristics of giant cell tumor of bone (GCTB) in Japan, and significant clinicopathological factors for predicting local recurrence. Clinicopathological profiles of 213 patients with GCTB (100 male, 113 female) involving extra‐craniofacial bones were retrieved. Pathological slides obtained at the initial surgery were reviewed. Fourteen pathological and five clinical features were statistically analyzed to disclose prognostic significance. Patient age ranged from 12–80 years (Average 38.7). Long bones were most frequently affected (86.4%), especially around the knee (62.9%). Histological features are basically similar to those previously reported. Within a follow‐up period (24–316 months, average 106.1 months), the local recurrence rate is 29.1%. Metastasis has occurred in 9 patients. Cox regression analysis of representative clinicopathological features shows that younger age, higher mitotic count, smaller zones of stromal hemorrhage, considerable vascular invasion and absence of ischemic necrosis are significant predictors for local recurrence. Initial operative method (curettage) is a significant risk factor in univariate analysis but not by multivariate analysis (P = 0.053). Denosumab administration increases risk but not significantly (P = 0.053). Histone 3.3 G34W immunopositivity is not significant for predicting local recurrence.

Giant Cell Tumor of Bone in Patients under 16 Years Old: A Single-Institution Case Series

Simple Summary

Giant cell tumor of the bone is a locally aggressive, rarely metastasizing tumor that accounts for about 5% of bone tumors; it generally occurs in patients between 20 and 45 years old. Sporadic cases (less than 140) have been described as occurring in the first two decades of life. A histone 3.3 (H3.3) gene, H3F3A, has been recently identified in as many as 96% of giant cell tumors of bone. These mutations are useful in the differential diagnosis of giant cell tumor of bone with its mimickers. The immunohistochemical expression of H3F3A resulted comparable to molecular analysis as reported in a recent investigation. In the present study, we describe our series of giant cell tumors of bone in pediatric patients <16 years old.

Abstract

Background: Giant cell tumor of bone is a locally aggressive, rarely metastasizing tumor that accounts for about 5% of bone tumors and generally occurs in patients between 20 and 45 years old. A driver mutation in the histone 3.3 (H3.3) gene H3F3A has been identified in as many as 96% of giant cell tumors of bone. The immunohistochemical expression of H3F3A H3.3 G34 expression was found in 97.8% of cases. In the present study, we describe our series of cases of giant cell tumor of bone in pediatric patients <16 years old. Methods: All cases of giant cell tumor of bone in pediatric patients <16 years old treated in our institute between 1982 and 2018 were reviewed. Immunohistochemistry and/or molecular analysis for H3F3A gene mutations was performed to confirm the diagnosis. A group of aneurysmal bone cysts in patients <16 years old was used as a control group. Results: Fifteen cases were retrieved. A pronounced female predominance (93%) was observed. A pure metaphyseal central location occurs in 2 skeletally immature patients. Conclusions: Giant cell tumor of bone should be distinguished from its mimickers due to differences in prognosis and treatment. Immunohistochemical and molecular detection of H3F3A gene mutation represents a reliable diagnostic tool.

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.

Preoperative CT for prediction of local recurrence after curettage of giant cell tumor of bone

•Preoperative CT images of GCTBs have value in prognostic prediction.•Certain features of GCTBs on CT images are related to local recurrence.•Our models' predictions for GCTB patients accepting extensive curettage are good.

Denosumab Treatment for Giant Cell Tumors, Aneurysmal Bone Cysts, and Fibrous Dysplasia-Risks and Benefits

PURPOSE OF REVIEW

This review summarizes current understanding of the role of denosumab, an inhibitor of receptor activator of nuclear kappa-B ligand (RANKL), in the management of 3 skeletal neoplasms: giant cell tumors, aneurysmal bone cysts, and fibrous dysplasia.

RECENT FINDINGS

A growing body of literature supports denosumab use in giant cell tumors, a neoplasm in which RANKL plays a clear pathogenic role. Comparatively less data is available in aneurysmal bone cysts and fibrous dysplasia; however, the pathogenic similarity of these disorders to giant cell tumors, as well as encouraging preliminary data, suggests denosumab may be useful. Denosumab's inhibitory effects on bone turnover are fully reversible after drug discontinuation. This raises important unanswered questions for clinical management, including potential risks of tumor recurrence and bone turnover rebound. Denosumab is a promising potential treatment for skeletal neoplasms. However, its clinical use is impacted by ongoing safety concerns related to postdiscontinuation rebound, particularly in children. There is a critical need to understand denosumab treatment and discontinuation effects on tumor recurrence and to develop strategies for long-term treatment in patients who cannot be managed surgically.

Bilateral Lung Metastases From a Phalangeal Giant Cell Tumor of Bone

We describe a rare pediatric case of a phalangeal giant cell tumor of bone with extensive bilateral lung metastases following curettage, wide resection, and amputation. Concurrent peripheral blood eosinophilia and pleural effusion with marked eosinophilia (47%) were present. To discover genetic changes driving tumor metastasis, genomic and transcriptome profiling of the metastatic lung mass as well as germline analysis were performed. Whole exome sequencing detected a histone H3F3A p.G35V missense mutation in tumor cells. RNA sequencing revealed overexpression of receptor activator of nuclear factor kappa-B ligand (RANKL). The patient is alive with no residual disease and uncompromised respiratory function 29 months after amputation of primary tumor and 19 months after surgical resection of his metastatic lung disease.

Giant Cell Tumor of Bone With Cartilage Matrix: A Clinicopathologic Study of 17 Cases

Giant cell tumor of bone (GCT) is a benign locally aggressive neoplasm composed of mononuclear cells admixed with innumerable osteoclast-type giant cells. H3F3A gene mutations producing mutant histone protein product H3.3 have been identified in 96% of GCT; mutant H3.3 is reliably demonstrated by immunohistochemistry. GCT may contain woven bone and rarely, neoplastic cartilage nodules which causes diagnostic challenges with aggressive neoplasms such as osteosarcoma. We describe the features of GCT with cartilage matrix and report the next-generation sequencing findings in a subset of tumors. Seventeen cases of GCT with cartilage matrix form the cohort: 7 males and 10 females, 13 to 55 (mean: 25) years old. Tumors involved the fibula (6), femur (6), and patella, tibia, humerus, S1, and scapula (1 case each). Tumors were radiolucent, circumscribed, lytic, and expansile. All contained classic GCT, foci of cartilage matrix, and trabeculae of woven bone. Immunohistochemistry showed diffuse staining for H3.3 in 9/9 cases and 1 case was positive for S100 and SOX9 in the cartilage areas. Next-generation sequencing showed a mutation in the H3F3A gene in 6/6 cases. On follow-up, 2 patients who underwent resection showed no disease after 12, and 7 months, respectively. Three patients had recurrences 10, 12, and 27 months after curettage; there were no metastases. GCT with cartilage matrix is uncommon. The cartilage matrix is associated with woven bone suggesting the neoplastic cells may differentiate into chondrocyte-like and osteoblast-like cells. Recognition of this neoplasm is important to prevent misdiagnosis and overtreatment of affected patients.

H3F3A G34 mutation DNA sequencing and G34W immunohistochemistry analysis in 366 cases of giant cell tumors of bone and other bone tumors

H3F3A mutations and the expression of glycine 34 to tryptophan (G34W) mutants in giant cell tumors of bone (GCTBs) and other bone tumors were detected to compare H3F3A mutation types and the expression of G34W-mutant protein in order to provide a theoretical basis for using H3F3A mutations as a diagnostic and differential-diagnostic tool for GCTBs. A total of 366 bone tumor cases were investigated. The cases involved 215 men and 151 women, whose median age was 29 years (3-84). The cases included GCTB (n=180), recurrent GCTB (n=19), GCTB with lung metastasis (n=5), pediatric GCTB (n=15), primary malignant GCTB (n=5), chondroblastoma (CB, n=61), chondrosarcoma grade II (n=15), dedifferentiated chondrosarcoma (n=17), chondromyxoid fibroma (n=9), aneurysmal bone cyst (n=9), nonossifying fibroma (n=9), osteosarcoma (n=16), and undifferentiated sarcoma (n=6). Sanger DNA sequencing analysis was used to detect H3F3A mutations. Immunohistochemistry was used to assess the expression of the G34W-mutated protein in these bone tumors. DNA sequencing results revealed H3F3A mutations in 95.00% of GCTBs (171/180), including glycine 34 to tryptophan (G34W, 163/180, 90.56%), glycine 34 to leucine (G34L, 3/180, 1.67%), glycine 34 to valine (G34V, 3/180, 1.67%), and glycine 34 to arginine (G34R, 2/180, 1.11%). Recurrent GCTBs mostly had the H3F3A G34W mutation (18/19, 94.74%), and GCTBs with lung metastasis all had the H3F3A G34W mutation (5/5, 100%). Pediatric GCTBs had a mutation rate of 93.33% (14/15), including one case with G34L. Four cases of primary malignant GCTB showed the H3F3A G34W mutation (4/5, 80.00%), and the classical GCTB component and malignant component showed consistent mutation types. Immunohistochemistry showed that GCTBs harboring G34W also expressed the mutant protein in tumor cell nuclei. Furthermore, one case of GCTB and one case of recurrent GCTB showed positive G34W immunostaining results despite being negative for the genetic mutation. Other bone tumors all showed wild-type expression in both DNA sequencing and immunohistochemistry. Our large-sample DNA sequencing analysis detected four different forms of mutations in GCTBs, including three rare mutation forms. The most common mutation of H3F3A was G34W, which was in accordance with the expression of G34W in GCTBs detected by immunohistochemistry. Although DNA sequencing analysis detected rare mutation types of H3F3A, false-negative results were also present due to the small number of cells in the samples. Detection of the most common (G34W) mutant protein by immunohistochemistry was more convenient. Given the high prevalence of these driver mutations, the detection of H3F3A mutant proteins can assist in the diagnosis of GCTB and its differential diagnosis from other bone tumors.

Fibrous Dysplasia/McCune-Albright Syndrome: A Rare, Mosaic Disease of Gα s Activation

Fibrous dysplasia/McCune-Albright syndrome (FD/MAS) is a rare disorder of striking complexity. It arises from somatic, gain-of-function mutations in GNAS, leading to mosaic Gα s activation and inappropriate production of intracellular cyclic adenosine monophosphate (cAMP). The clinical phenotype is largely determined by the location and extent of affected tissues, and the pathophysiological effects of Gα s activation within these tissues. In bone, Gα s activation results in impaired differentiation of skeletal stem cells, leading to discrete skeletal lesions prone to fracture, deformity, and pain. Extraskeletal manifestations include a variable combination of hyperpigmented macules and hyperfunctioning endocrinopathies. Distinctive age-related changes in disease development has key effects on histologic, radiographic, and clinical features. FD/MAS thus presents along a uniquely broad clinical spectrum, and the resulting challenges in diagnosis and management can be difficult for clinicians. This review presents FD/MAS in the context of a mosaic disorder of Gα s activation, providing an intellectual framework within which to understand, evaluate, and treat this interesting disease. It includes a comprehensive summary of current understanding of FD/MAS pathogenesis, and a detailed discussion of clinical presentation and management. Critical areas of unmet need are highlighted, including discussion of key challenges and potential solutions to advance research and clinical care in FD/MAS.

Soft Tissue Special Issue: Giant Cell-Rich Lesions of the Head and Neck Region

Giant cell-rich lesions represent a heterogeneous group of tumors and non-neoplastic lesions, usually arising in bone, which harbor varying number of reactive osteoclastic-type multinucleate giant cells as a common feature. Among these entities, some are confined to the head and neck region (e.g., central giant cell granuloma and mimicking lesions, i.e., peripheral giant cell granuloma and cherubism) or show a relative predilection for this region (e.g., aneurysmal bone cyst and brown tumor of hyperparathyroidism), while others are rare but associated with distinct underlying disease (e.g., giant cell tumor of bone) or histology (e.g., tenosynovial giant cell tumor of the temporomandibular joint and phosphaturic mesenchymal tumor of the jaws) when occurring in the head and neck. Collectively, these lesions pose great challenge in the pathologic diagnosis, which often requires combinatory assessment from the clinical, histopathologic, and/or molecular aspects. This review provides a summary of pertinent clinical and pathologic features and an update of recent molecular and genetic findings of these entities. The considerations in differential diagnosis as well as the effects of the emerging therapeutic RANKL-antagonizing antibody denosumab will also be addressed.

Absence of H3F3A mutation in a subset of malignant giant cell tumor of bone

Giant cell tumor of bone typically involves the epiphysis of the long bones of skeletally mature patients. It is genetically characterized by highly recurrent and specific mutations of the H3F3A gene, which encodes histone H3.3. The most common mutation H3F3A G34W can readily be detected by a recently developed mutation-specific antibody. Giant cell tumor of bone rarely transforms to a sarcoma (malignant giant cell tumor of bone), which has not been genetically characterized in detail. We studied seven clinicopathologically defined malignant giant cell tumors, as well as two H3F3A-mutant bone sarcomas without giant cell tumor histology using a combination of clinicopathological, immunohistochemical, and molecular methods (Sanger sequencing + pyrosequencing or next generation sequencing). The cases included five men and four women, with a median age at initial diagnosis of 27 years. The two H3F3A G34W-positive sarcomas without giant cell tumor histology involved the subarticular epiphyseal sites, suggesting relatedness with giant cell tumor of bone. In two of the seven clinicopathologically defined malignant giant cell tumor cases, the sarcoma tissue showed the H3F3A G34W mutation. However, in the remaining five cases, in contrast to their associated H3F3A G34W-mutant giant cell tumor, the sarcoma lacked the H3F3A G34W mutation, either entirely or sub-clonally in the samples tested. This discordant mutation status was confirmed in all instances by immunohistochemistry and sequencing. A FISH analysis suggested that the absence of the H3F3A G34W mutation may be related to deletion of the H3F3A gene. Therefore, we have demonstrated that H3F3A G34W mutation, a critical driver in giant cell tumor, is absent in a subset of malignant giant cell tumor of bone. This novel recurrent phenomenon has potential biological and diagnostic implications, and further study is required to better characterize this progression pathway and understand its mechanism.

Chondroblastomas presenting in adulthood: a study of 39 patients with emphasis on histological features and skeletal distribution

AIMS

Chondroblastomas (CB) are rare bone tumours that typically arise in the epiphysis/apophysis of long bones in skeletally immature patients. We explore the clinicopathological features of CB presenting in adults.

METHODS AND RESULTS

CB in patients ≥20 years of age were retrieved from our institutional archives. Thirty-nine CB were identified (29 male/10 female; aged 20-54 years). Twenty (51%) cases occurred in long tubular bones, 10 (26%) in small bones of the feet, five (13%) in flat bones and four (10%) in the patella. All cases showed classic cytological features of CB, and chondroid matrix was universally present. Calcification was identified in 10 cases (26%), including various combinations of serpiginous (n = 7), punctate (n = 6), classic chicken-wire (n = 4) and psammomatous (n = 2) patterns. Haemosiderin (n = 19), woven bone (n = 13), secondary aneurysmal bone cyst formation (n = 8), foamy macrophages (n = 4), hyalinised vascular spaces (n = 2) and cholesterol clefts (n = 2) were noted. Follow-up information (n = 32, 1-452 months) revealed local recurrence in three patients, all >40 years of age with flat bone origin, one of which developed pulmonary metastases 132 months after initial diagnosis.

CONCLUSIONS

CB in patients >20 years of age more frequently involves the short bones of the hands/feet and flat bones compared to those arising in their younger counterparts. A subset may harbour extensive serpiginous or psammomatous calcification rather than the classic chicken-wire pattern. Although the overall local recurrence rate in adulthood is approximately 10%, all three patients with recurrent disease had tumours involving flat bones, suggesting that tumours arising in these sites may behave more aggressively.

[New aspects on giant cell tumor of bone]

A giant cell tumor of bone (GCTB) is one of the giant cell-rich lesions of bone and has to be differentiated from non-ossifying fibroma, aneurysmatic bone cyst, chondroblastoma, "brown tumor" and osteosarcoma containing giant cells. A hallmark of GCTB is the presence of the distinct histone 3 (H3F3A) mutation G34W and its detection either by sequencing methods or using immunohistochemistry with a novel antibody against this mutational site. Worrisome is the fact that under denosumab therapy a histological change of the lesions can be seen and there are first reports of sarcomas arising after therapy. When diagnosing giant cell-rich lesions, pathologists should be aware of the various differential diagnoses and morphological spectrum within GCTB.

Clinical features and prognostic factors of pediatric spine giant cell tumors: report of 31 clinical cases in a single center

BACKGROUND CONTEXT

Giant cell tumors (GCTs) of the bone are benign but locally aggressive. Pediatric spine giant-cell tumors (PSGCTs) have been infrequently reported in the literature because of the rarity of the disease.

PURPOSE

The purpose of this study was to define the overall occurrence rate of PSGCTs among all spinal GCTs in our center and investigate the clinical features and prognostic factors of this rare disease.

STUDY DESIGN

A retrospective review.

PATIENT SAMPLE

Thirty-one PSGCT patients, screened from 226 patients with spine GCTs who received treatment in our center between 1998 to 2017.

OUTCOME MEASURES

The clinical symptoms, neurologic status, radiologic manifestations, treatment, outcome, and complications were recorded and analyzed.

METHODS

The postoperative recurrence-free survival (RFS) rate was estimated by the Kaplan-Meier method. Factors with p values ≤.1 were subjected to multivariate analysis for RFS by proportional hazard analysis, among which p values ≤.05 were considered statistically significant.

RESULTS

A total of 31 (31 of 226, 13.7%) PSGCTs patients (9 male and 22 female) were included in the study, with a mean age of 15.9 years and a mean follow-up period of 85.1 (median 84.0; range 12-221) months. The majority of patients (80.6 %) were 14-18 years of age. Recurrence was detected in 12 (38.7%) of the 31 patients. Univariate and multivariate analyses suggested that Jaffe grade II-III was an adverse prognostic factor for RFS, while total spondylectomy and bisphosphonate treatment were positive prognostic factors.

CONCLUSIONS

Total en bloc spondylectomy (TES) is associated with excellent prognosis for PSGCTs, and total piecemeal spondylectomy is a viable alternative if total en bloc spondylectomy is unfeasible. Long-term bisphosphonate administration could significantly reduce the recurrence risk of PSGCTs. Denosumab treatment is recommended, especially for advanced PSGCTs. Jaffe grade II-III is an adverse prognostic factor for recurrence.

Similar local recurrence but better function with curettage versus resection for bone giant cell tumor and pathological fracture at presentation

BACKGROUND

There are conflicting reports for the outcome of the patients with giant cell tumor of bone (GCTB) and pathological fracture at presentation treated with curettage or resection. This study compared local recurrence, complications, and function after curettage versus resection for these patients.

MATERIALS AND METHODS

We retrospectively studied the files of 46 patients with histologically confirmed GCTB of the extremities admitted and treated from 1982 to 2015. The median follow-up was 79.5 months (57.0-125.5 months). We evaluated local recurrence and type of surgery-related complications with imaging and function with the Musculoskeletal Tumor Society (MSTS) score.

RESULTS

Overall local recurrence was 6.5%. There were one patient with curettage and two patients with resection; local recurrence rate was similar between the two procedures but the time to local recurrence was shorter after curettage. MSTS score was significantly better after curettage. Complications occurred in two patients after curettage and in five patients after resection; because of the low number of patients with complications, a statistical comparison was not possible; however, by direct comparison of the numbers, complications were more common after resection compared with curettage.

CONCLUSION

Curettage is recommended for GCTB and pathological fracture at presentation because of similar local recurrence but better function compared with resection. The treating physicians should be aware and inform their patients for a shorter time to local recurrence after curettage and for more complications after resection.

Histopathology of giant cell tumors of the bone: With special emphasis on fibrohistiocytic and aneurysmal bone cyst like components

Objective

The aim of this study was to define histopathological features of giant cell tumor of bone, especially accompanying fibrohistiocytic or aneurysmal bone cyst like components, in the light of our institutions experience.

Methods

A total of 120 cases (64 females and 56 males; mean age: 36.2 (12–80)) with ‘GCT’ diagnosed between the years 1996–2016 were included in this retrospective analysis. Cases were evaluated according to clinical features such as age, gender, localization, recurrence, metastasis and histopathological features.

Results

Tumors were localized most frequently at proximal tibia and distal femur, respectively. In 11 cases areas rich in fibrohistiocytic component and in 20 cases aneurysmal bone cyst like component were observed. In 2 cases both components were present. Twenty three cases recurred. In 1 case which was primarily located at calcaneus, tumor metastasized to lung 4 years later during follow-up.

Conclusion

GCT can be confused with other tumor or tumor-like lesions involving giant cells. Secondary changes such as fibrohistiocytic or aneurysmal bone cyst-like components and coagulation necrosis were frequently seen in conventional giant cell tumor of bone. For tumors having prominent fibrohistiocytic and/or aneurysmal bone cyst-like components, in order to detect characteristic areas representing GCT, additional sampling is essential. Although secondary histopathological changes do not appear to affect clinical outcome, these features are important in differential diagnosis. Approximately one fifth of GCT cases show recurrence and sacrum and foot bones were the most frequent sites for recurrence.

Level of evidence

Level IV, diagnostic study.

Updates in Primary Bone Tumors: Current Challenges and New Opportunities in Cytopathology

The review summarizes the current diagnostic challenges in fine-needle aspiration of primary bone tumors, with focus on the application of new molecular and immunohistochemical techniques in the diagnosis of giant cell-rich neoplasms, chondrosarcomas, and notochordal tumors.

Immunohistochemistry for histone H3G34W and H3K36M is highly specific for giant cell tumor of bone and chondroblastoma, respectively, in FNA and core needle biopsy

BACKGROUND

Diagnosing giant cell-rich bone tumors can be challenging on limited biopsies. H3 histone family member 3A (H3F3A) (G34W/V/R/L) mutations are present in the majority of giant cell tumors (GCTs) of bone and H3 histone family member 3B (H3F3B) (K36M) mutations are present in nearly all chondroblastomas, but are absent in histologic mimics. Mutation-specific immunohistochemistry (IHC) is highly specific for GCT and chondroblastoma in surgical excisions. The objective of the current study was to validate H3G34W and H3K36M IHC in the diagnosis of giant cell-rich bone tumors on fine-needle aspiration and core needle biopsy specimens.

METHODS

IHC was performed using monoclonal antibodies against histone H3.3 G34W and K36M in GCTs of bone (26 cases, including 2 malignant cases), GCT of Paget disease (1 case), chondroblastoma (8 cases), aneurysmal bone cyst (7 cases), and osteosarcoma (13 cases) with available fine-needle aspiration and/or core needle biopsy specimens from 2 institutions. H3F3A and H3F3B Sanger sequencing was performed on all 4 H3G34W IHC-negative GCTs.

RESULTS

IHC for H3G34W was positive in 22 of 26 GCTs (85%) and negative in all histologic mimics. IHC for H3K36M was positive in all 8 chondroblastomas and negative in all histologic mimics. IHC results were concordant between biopsy and surgical specimens in 152 of 158 samples (96%). Sequencing identified alternate H3F3A G34L and G34V mutations in 1 IHC-negative GCT each, but no mutation was found in the remaining 2 cases.

CONCLUSIONS

H3G34W and H3K36M IHC is highly specific for GCT and chondroblastoma, respectively, among giant cell-rich bone tumors, and is useful for confirming the diagnosis in limited biopsies. The presence of alternate H3F3A mutations accounts for the H3G34W IHC negativity in a subset of GCT of bone cases. Cancer Cytopathol 2018. © 2018 American Cancer Society.

Giant Cell Tumor of Bone in Patients 55 Years and Older: A Study of 34 Patients

OBJECTIVES

Most giant cell tumors of bone (GCTs) occur in patients aged 20 to 40 years. We analyzed features of GCT in patients 55 years or older.

METHODS

GCTs were examined for fibrosis, matrix, cystic change, histiocytes, mitoses, and necrosis. Clinical/radiologic data were collected.

RESULTS

Thirty-four (5%) of 710 GCTs occurred in patients older than 55 years (14/20 male/female; 56-83 years) in long bones (n = 24), vertebrae (n = 6), pelvis (n = 3), and metacarpal (n = 1). Imaging was classic in 26 of 27 cases; one case appeared malignant. Morphologic patterns included fibrosis (n = 29), bone formation (n = 19), cystic change (n = 8), necrosis (n = 8), foamy histiocytes (n = 7), and secondary aneurysmal bone cyst formation (n = 1). Mitoses ranged from 0 to 18 per 10 high-power fields. Six recurred; one patient developed metastasis. Four of five cases harbored H3F3A mutations.

CONCLUSIONS

GCTs in patients 55 years or older share pathologic characteristics with those arising in younger adults. Fibrosis and reactive bone are common, potentially leading to diagnostic confusion in this population. No histologic features correlate with adverse outcome.

H3F3A (Histone 3.3) G34W Immunohistochemistry: A Reliable Marker Defining Benign and Malignant Giant Cell Tumor of Bone

Giant cell tumor of bone (GCTB) is a locally aggressive subarticular tumor. Having recently reported that H3.3 G34W mutations are characteristic of this tumor type, we have now investigated the sensitivity and specificity of the anti-histone H3.3 G34W rabbit monoclonal antibody in a wide variety of tumors including histologic mimics of GCTB to assess its value as a diagnostic marker. We also determined the incidence of H3.3 G34 mutations in primary malignant bone tumors as assessed by genotype and H3.3 G34W immunostaining. A total of 3163 tumors were tested. Totally, 213/235 GCTB (90.6%) showed nuclear H3.3 p.G34W immunoreactivity. This was not the case for the rare variants, p.G34L, M, and V, which occurred most commonly in the small bones of the hands, patella, and the axial skeleton. If these sites were excluded from the analysis, H3.3 G34W expression was found in 97.8% of GCTB. Malignant bone tumors initially classified as osteosarcomas were the only other lesions (n=11) that showed G34W expression. Notably an additional 2 previously reported osteosarcomas with a p.G34R mutation were not immunoreactive for the antibody. A total of 11/13 of these malignant H3.3-mutant tumors exhibited an osteoclast-rich component: when imaging was available all but one presented at a subarticular site. We propose that subarticular primary malignant bone sarcoma with H3.3 mutations represent true malignant GCTB, even in the absence of a benign GCTB component.

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.