GNAS mutational analysis in differentiating fibrous dysplasia and ossifying fibroma of the jaw

Whole Exome Sequencing as an Effective Molecular Diagnosis Tool for Craniofacial Fibrous Dysplasia with Ocular Complications

PURPOSE

To summarize the clinical manifestations of craniofacial fibrous dysplasia (CFD) patients with ocular complications, and find effective methods to diagnose early.

METHODS

Nine CFD patients with ocular complications, and their parents were recruited in this study. All patients underwent ocular and systemic examinations. Bone lesions from all patients and peripheral blood from patients and their parents were collected for whole exome sequencing (WES). According to the screening for low-frequency deleterious variants, and bioinformatics variants prediction software, possible disease-causing variants were found in multiple CFD patients. The variants were validated by Sanger sequencing. Trio analysis was performed to verify the genetic patterns of CFD.

RESULTS

All patients were diagnosed with CFD, according to the clinical manifestations, classic radiographic appearance, and pathological biopsy. The main symptoms of the 9 CFD patients, included visual decline (9/9), craniofacial deformity (3/9) and strabismus (2/9), with few extraocular manifestations. The family backgrounds of all the CFD patients indicated that only the patient was affected, and their immediate family members were normal. GNAS variants were identified in all bone lesions from CFD patients, including two variant types: c.601C > T:p.R201C(6/9) and c.602G > A:p.R201H (3/9) in exon 8. The detection rate reached 100% by WES, but only 77.8% by Sanger sequencing. Interestingly, we found GNAS variants could not be detected in peripheral blood samples from CFD patients or their parents, and other potentially disease-causing gene variants related to CFD were not found.

CONCLUSIONS

For CFD patients with bone lesions involving the optic canal or sphenoid sinus regions, ocular symptoms should also be considered. Furthermore, we confirmed that CFD is not inherited, somatic variants in the GNAS gene are the main pathogenic gene causing CFD. Compared to the traditional methods in molecular genetic diagnosis of CFD, WES is more feasible and effective but limited in the type of samples.

Pediatric Gnathic Bony and Mesenchymal Tumors

Evaluation of bone pathology within the head and neck region, particularly the gnathic bonesis is complex, demonstrating unique pathologic processes. In part, this variation is due to odontogenesis and the embryological cells that may be involved, which can contribute to disease development and histologic variability. As with any boney pathosis, the key is to have clinical correlation, particularly with radiographic imaging prior to establishing a definitive diagnosis. This review will cover those entities that have a predilection for the pediatric population, and while it is not all inclusive, it should serve as a foundation for the pathologist who is evaluating bony lesions involving the craniofacial skeleton.

Genomic Profiling of the Craniofacial Ossifying Fibroma by Next-Generation Sequencing

BACKGROUND

Ossifying fibroma (OF) of the craniofacial skeleton is a fibro-osseous lesion characterized by various patterns of bone formation in a cellular fibroblastic stroma. The molecular landscape of OF remains mostly unknown. There are a few known pathogenic abnormalities in OF, including HRPT2 mutations in conventional OF and SATB2 translocations in juvenile psammomatoid OF. On the other hand, conflicting reports exist regarding MDM2 gene amplification and chromosomal copy number alterations (CNA) in OF.

METHODS

Surgically removed biopsies and curettage specimens from OF patients were obtained. Clinical, radiographic, and pathologic features of tumors were reviewed. Genomic DNA was extracted from formalin-fixed, paraffin-embedded blocks of tumor tissue. Capture-based DNA next-generation sequencing targeting the coding regions 529 cancer genes and select introns was performed.

RESULTS

We identified 17 OF cases from 8 male and 8 female patients with mean age of 22 years (range 1-58 years). Nine case occurred in the gnathic bones and 8 in the extragnathic craniofacial bones. These cases included 3 juvenile psammomatoid OF, 6 conventional OF and 8 juvenile trabecular OF. Large-scale CNAs were present in 6 of 17 cases. Seven cases (41%) had focal amplifications including FOSB (n = 2, 11%), FOS (n = 4, 23%), COL1A1 (n = 4, 23%) and TBX3 (n = 5, 29%). Three cases (17%) had pathogenic CDC73 mutations. No cases showed focal MDM2 amplification.

CONCLUSIONS

Here, we provided a comprehensive molecular characterization of OF that reveals a heterogeneous genetic profile with occasional large-scale CNAs (n = 6, 35%). FOS, FOSB, and TBX3 genes that regulate AP-1 transcriptional complex are frequently altered in OF (n = 7, 41%), chiefly in juvenile trabecular OF. These genes encode transcription factors that act as downstream effectors of the MAP kinase signaling pathway. MDM2 amplification is an exceedingly rare event in OF, if present at all, so identification of this event should continue to raise concern for low-grade gnathic osteosarcoma. In summary, our findings suggest that OF represents a heterogeneous group of tumors at the genetic level but dysregulation of the AP-1 pathway may play a role in pathogenesis of juvenile trabecular OF.

Fibrous Dysplasia of the Jaw: Advances in Imaging and Treatment

A total of 7% of all benign bone lesions are diagnosed as fibrous dysplasia (FD). The symptoms of FD of the jaw range from asymptomatic to dental anomalies, pain and facial asymmetry. Due to its resemblance to other fibro-osseous bone lesions, misdiagnosis often occurs and can lead to inadequate treatment. Particularly in the jaw, this lesion does not become quiescent during puberty, making fundamental knowledge about the diagnosis and treatment of FD crucial. Mutational analysis and nonsurgical approaches offer new diagnostic and therapeutic options. In this review, we examine the advances and the difficulties of the diagnosis and the various treatment modalities of FD of the jaw in order to capture the current scientific knowledge on this bone disease.

Cemento-Osseous Dysplasia of the Jaw: Demographic and Clinical Analysis of 191 New Cases

Cemento-osseous dysplasia (COD) is a form of benign fibro-osseous lesion of the jaw. We sought to evaluate the demographic and clinical presentations of COD by collecting and analyzing the demographic, clinical, radiographic, and pathologic data of COD diagnosed in our institution from 2017 to 2022. Over this six-year period, the records of 191 patients with COD were reviewed. Most patients were African American and female. Eighty-five patients were diagnosed with florid COD (FLCOD), 63 with periapical COD (PCOD), and 43 with focal COD (FCOD). Twenty-eight (14.7%) patients presented symptoms. The most common symptom was pain. All the symptomatic cases of COD that were histopathologically diagnosed were osteomyelitis in the setting of COD. Symptomatic patients were older (mean of 61.3 years) than the asymptomatic patients (mean of 51.2 years). Due to the radiographic appearance of a radiolucency or a mixture of radiolucency and radiopacity, forty-five asymptomatic patients were biopsied. Most of the asymptomatic patients biopsied were patients with FCOD (n = 19, 54.3%), followed by PCOD (n = 16, 25.8%), and FLCOD (n = 10, 15.2%). FLCOD is the most common form of COD to present with symptoms. Due to the significant overlap in clinical and radiographic presentation with other entities, FCOD and PCOD remain a diagnostic challenge to dentists. In conclusion, we analyzed the demographic and clinical features of 191 new cases of COD, which reaffirms that cemento-osseous dysplasia is a condition that primarily affects middle-aged females of African descent and occurs more frequently in the mandible.

PTHrP Modulates the Proliferation and Osteogenic Differentiation of Craniofacial Fibrous Dysplasia-Derived BMSCs

Fibrous dysplasia (FD) is a skeletal stem cell disease caused by mutations in the guanine nucleotide-binding protein, alpha-stimulating activity polypeptide (GNAS) gene, which results in the abnormal accumulation of cyclic adenosine monophosphate (cAMP) and hyperactivation of downstream signaling pathways. Parathyroid hormone-related protein (PTHrP) is secreted by the osteoblast lineage and is involved in various physiological and pathological activities of bone. However, the association between the abnormal expression of PTHrP and FD, as well as its underlying mechanism, remains unclear. In this study, we discovered that FD patient-derived bone marrow stromal cells (FD BMSCs) expressed significantly higher levels of PTHrP during osteogenic differentiation and exhibited greater proliferation capacity but impaired osteogenic ability compared to normal control patient-derived BMSCs (NC BMSCs). Continuous exogenous PTHrP exposure on the NC BMSCs promoted the FD phenotype in both in vitro and in vivo experiments. Through the PTHrP/cAMP/PKA axis, PTHrP could partially influence the proliferation and osteogenesis capacity of FD BMSCs via the overactivation of the Wnt/β-Catenin signaling pathway. Furthermore, PTHrP not only directly modulated cAMP/PKA/CREB transduction but was also demonstrated as a transcriptional target of CREB. This study provides novel insight into the possible pathogenesis involved in the FD phenotype and enhances the understanding of its molecular signaling pathways, offering theoretical evidence for the feasibility of potential therapeutic targets for FD.

Cemento-osseous dysplasia is caused by RAS-MAPK activation

Cemento-osseous dysplasia (COD) belongs to the spectrum of benign fibro-osseous lesions occurring exclusively in the tooth-bearing areas of the jaws. Depending on site and extent of involvement, periapical, focal and florid subtypes can be distinguished that share an identical histomorphology. Most cases are asymptomatic and follow a self-limited course requiring no specific treatment. Over time, lesions progressively mineralise while the cellularity decreases. However, the molecular pathogenesis of COD, has not yet been explored. We analysed a series of 31 COD samples by targeted sequencing and detected pathogenic hotspot mutations involving the RAS-MAPK signalling pathway in 5/18 evaluable cases (28%). The mutations were found in the BRAF, HRAS, KRAS, NRAS, and FGFR3 genes. Our findings suggest that COD is driven by RAS-MAPK activation; however, the mechanism underlying the spontaneous growth arrest typically occuring in most of the lesions remains elusive.

Fibrocartilaginous mesenchymoma of pelvis-a potential diagnostic pitfall

Fibrocartilaginous mesenchymoma (FM) is a rare bone tumor mimicking other fibrocartilaginous lesions on imaging and histologically. Hence, it is difficult to diagnose this entity especially on small biopsies. In this article, we report a case of FM mimicking desmoplastic fibroma on biopsy. A 36-year-old male presented with pain in the left hip. Imaging showed a large expansile lytic lesion involving the acetabulum and pubis. The differential diagnosis was suggestive of giant cell tumor, aneurysmal bone cyst, intraosseous desmoplastic fibroma, and chondrosarcoma. Biopsy revealed a low-grade spindle cell lesion with no evidence of osteoid or chondroid matrix. The lack of cartilaginous nodules in the biopsy prompted a preoperative diagnosis of desmoplastic fibroma. The excised mass showed bland spindle cell proliferation, benign cartilage nodules, and epiphyseal plate-like enchondral ossification suggestive of fibrocartilaginous mesenchymoma. Negative immunostaining for SATB2, CDK4, and MDM2 ruled out low-grade central osteosarcoma. Though GNAS mutations were not performed in this case, rimming of the bony trabeculae at the periphery of the epiphyseal growth plate-like cartilaginous nodule ruled out fibrous dysplasia. The absence of cartilaginous component misleads the diagnosis preoperatively in small biopsies.

Psammomatoid Ossifying Fibroma Is Defined by SATB2 Rearrangement

Psammomatoid ossifying fibroma (PsOF), also known as juvenile PsOF, is a benign fibro-osseous neoplasm predominantly affecting the extragnathic bones, particularly the frontal and ethmoid bones, with a preference for adolescents and young adults. The clinical and morphologic features of PsOF may overlap with those of other fibro-osseous lesions, and additional molecular markers would help increase diagnostic accuracy. Because identical chromosomal breakpoints at bands Xq26 and 2q33 have been described in 3 cases of PsOF located in the orbita, we aimed to identify the exact genes involved in these chromosomal breakpoints and determine their frequency in PsOF using transcriptome sequencing and fluorescence in situ hybridization (FISH). We performed whole RNA transcriptome sequencing on frozen tissue in 2 PsOF index cases and identified a fusion transcript involving SATB2, located on chromosome 2q33.1, and AL513487.1, located on chromosome Xq26, in one of the cases. The fusion was validated using reverse transcription (RT)-PCR and SATB2 FISH. The fusion lead to a truncated protein product losing most of the functional domains. Subsequently, we analyzed an additional 24 juvenile PsOFs, 8 juvenile trabecular ossifying fibromas (JTOFs), and 11 cemento-ossifying fibromas (COFs) for SATB2 using FISH and found evidence of SATB2 gene rearrangements in 58% (7 of 12) of the evaluable PsOF cases but not in any of the evaluable JTOF (n = 7) and COF (n = 7) cases. A combination of SATB2 immunofluorescence and a 2-color SATB2 FISH in our index case revealed that most tumor cells harboring the rearrangement lacked SATB2 expression. Using immunohistochemistry, 65% of PsOF, 100% of JTOF, and 100% of COF cases showed moderate or strong staining for SATB2. In these cases, we observed a mosaic pattern of expression with >25% of the spindle cells in between the bone matrix, with osteoblasts and osteocytes being positive for SATB2. Interestingly, 35% (8 of 23) of PsOFs, in contrast to JTOFs and COFs, showed SATB2 expression in <5% of cells. To our knowledge, this is the first report that shows the involvement of SATB2 in the development of a neoplastic lesion. In this study, we have showed that SATB2 rearrangement is a recurrent molecular alteration that appears to be highly specific for PsOF. Our findings support that PsOF is not only morphologically and clinically but also genetically distinct from JTOF and COF.

GNAS mutation analysis assists in differentiating chronic diffuse sclerosing osteomyelitis from fibrous dysplasia in the jaw

Chronic diffuse sclerosing osteomyelitis of the mandible (DSOM) and fibrous dysplasia (FD) are distinct lesions with overlapping clinicopathological features that complicate their diagnosis. This study aimed to evaluate the efficacy of GNAS mutation analysis in differentiating between these two conditions. DNA samples from patients with DSOM (n = 35) and FD (n = 29) were collected to analyze the presence of GNAS mutations in exons 8 and 9, the two previously reported hotspot regions, using polymerase chain reaction and direct sequencing. Twenty-four of 29 patients (83%) with FD showed missense mutations in codon 201 in exon 8, whereas no mutation was detected in exon 9. No mutations were found in any of the 35 cases with DSOM. We also identified one case with an uncertain diagnosis due to overlapping clinicopathological features of DSOM and FD. A Q227H mutation was detected in this case, that confirmed the diagnosis of FD. Taken together, the findings indicate that mutational analysis of the GNAS is a reliable approach to differentiate between DSOM and FD of the jaw.

A two-generation hyperparathyroidism-jaw tumor (HPT-JT) syndrome family: clinical presentations, pathological characteristics and genetic analysis: a case report

Background

Hyperparathyroidism-Jaw Tumor (HPT-JT) is caused by inactivating germline mutations of CDC73. This hereditary disease can present with a range of symptoms. Jaw ossifying fibroma (OF) is one of the most important clinical presentations, affecting 30% of HPT-JT patients. However, OF is easily confused with other fibro-osseous lesions (FOLs) of the jaw. The correct diagnosis of HPT-JT is a real challenge and must be confirmed by genetic testing.

Case presentation

A female proband and her father suffered from multiple and recurrent FOLs in the jaw. Considering well demarcated margin and heterogeneous calcified substance lying in a variable density of fibrous stroma, we reached the diagnosis of jaw OF through radiologic and microscopic analyses. Additionally, the proband presented with chronic anemia resulting from menorrhagia, as well as renal mixed epithelial and stromal tumor (MEST). Two patients both presented with no evidence of Hyperparathyroidism (HPT). A germline start codon mutation (c.1A > G) of CDC73 was identified in them. Copy number loss at the CDC73 gene locus was verified in the jaw tumor sample of the proband.

Conclusion

Regardless of whether HPT manifestations are present, patients with heritable jaw OF may be at risk for HPT-JT. Genetic testing should be adopted to confirm the diagnosis. Early recognition of HPT-JT helps to better develop tailored treatment plans and surveillance programs.

MDM2 Gene Amplification and Expression of MDM2 and CDK4 are Rare in Ossifying Fibroma of Craniofacial Bones

Ossifying fibroma of the craniofacial bones is a fibro-osseous lesion characterized by varied patterns of bone formation in a fibroblastic stroma. Ossifying fibroma is a putatively benign lesion with no reports of malignant transformation or metastasis. Differentiation from other fibro-osseous lesions can be challenging necessitating synthesis of clinical, radiological and pathological findings. The molecular pathogenesis of ossifying fibroma is poorly understood but recent studies have reported MDM2 gene amplification and chromosomal copy number changes in a subset of ossifying fibromas. MDM2 amplification in ossifying fibroma, if true, presents a diagnostic problem because this genetic event, at least among craniofacial fibro-osseous lesions, was previously considered specific for low-grade osteosarcoma. In the present study, we investigated the utility of MDM2 and CDK4 immunohistochemistry, and fluorescence in situ hybridization for MDM2 gene amplification, in the diagnosis of 44 craniofacial bone ossifying fibromas. Focal MDM2 and CDK4 nuclear immunoreactivity was found in 11 and 1 ossifying fibromas, respectively, but none demonstrated MDM2 amplification by fluorescence in situ hybridization. A single tumor displayed MDM2 amplification without nuclear immunoreactivity to either MDM2 or CDK4. Our data suggest that while focal MDM2 and CDK4 nuclear expression may be detected in a minority of ossifying fibromas, this expression does not correlate with MDM2 amplification. In addition, MDM2 amplification is extremely rare in ossifying fibroma so the detection of this genetic abnormality should continue to raise concern for osteosarcoma.

[Clinicopathological analysis of 105 patients with fibrous dysplasia of cranio-maxillofacial region]

OBJECTIVE

To compare the clinicopathologic features and prognosis of the different types of fibrous dysplasia (FD) of cranio-maxillofacial region, so as to provide a new reference for clinicians to treat these patients and make prognostic judgement.

METHODS

Clinical records, radiographic data and pathological information of 105 patients diagnosed with FD or McCune-Albright syndrome (MAS) at the Department of Oral Pathology, Peking University Hospital of Stomatology from January 2013 to December 2020 were collected. The patients were divided into 4 groups: monostotic FDs, polyostotic FDs, MAS and a specific type called craniofacial fibrous dysplasia (CFD) limited in the craniofacial region. The clinicopathological characteristics, treatment and follow-up data of each type were analyzed.

RESULTS

Of all the 105 patients, 46 were males and 59 were females, with a male-to-female ratio of 1 ∶1.3. The onset age ranged from 0 to 56 years and the median age was 12 years. On the basis of different involvement conditions, 4 types were divided. The most common type was monostotic FDs (43 cases, 40.95%), including maxilla (29 cases), mandibular (12 cases) and zygoma (2 cases). 32 cases (30.48%) were diagnosed with polyostotic FDs, 7 cases (6.67%) were MAS, and 23 cases (21.90%) were CFDs confirmed by computed tomography (CT) analysis. CFD was clearly distinct from other types of FD, such as the patient gender and the serum alkaline phosphatase level in peripheral blood before operative surgery. The pathologic findings of various types FD were quite similar, whilst the predominant fibrous tissue hyperplasia could be observed in polyostotic FDs and MAS types.

CONCLUSION

The clinicopathologic features of FD in the cranio-maxillofacial region are different from the FD lesions in other parts of the body. The clinicopathological features of CFD are significantly different from those of monostotic and polyostotic FDs in the cranio-maxillofacial region. Therefore, the clinicians should pay attention to distinguish CFD in clinic, imaging and pathology aspects, so as to further clarify its features in clinic management and prognosis.

First presentation of a frameshift mutation in the SETD2 gene of a juvenile psammomatoid ossifying fibroma (JPOF) associated with an aneurysmal bone cyst

Background

The rarity of juvenile psammomatoid ossifying fibroma (JPOF) and lack of cytogenetic studies prompted us to report a novel SETD2 gene mutation in a benign odontogenic tumour.

Case presentation

A 21-year-old man presented with a hard, expanded mandibular cortex. Computed tomography revealed multilocular radiopacity in the mandible; this was reconstructed via segmental mandibulectomy using a vascularised iliac crest flap. Based on the clinical and histological findings, we diagnosed JPOF associated with an aneurysmal bone cyst. Microscopically, the solid area was characterised by many rounded or angular ossicles in a cellular fibrous stroma. The stromal cells were spindle-like or stellate. Next-generation sequencing detected a frame shift mutation of the SETD2 gene, while the copy number was normal.

Conclusions

Our findings suggest further genetic studies should be performed to assess whether this mutation is related to tumour genesis. 

Juvenile Granulosa Cell Tumor as the Presenting Feature of McCune-Albright Syndrome

Introduction

GNAS mutations have been reported in both McCune-Albright syndrome (MAS) and juvenile granulosa cell tumors (JGCT) but have never been reported simultaneously in the same patient.

Case Presentation

A 15-year-old girl developed secondary oligomenorrhea. Laboratory studies revealed suppressed gonadotropin levels with markedly elevated estradiol and inhibin B levels. Pelvic ultrasound showed a 12-cm heterogeneous right adnexal mass; pelvic magnetic resonance imaging to further characterize the mass displayed heterogeneous bilateral femoral bone lesions initially concerning for metastatic disease. Positron emission tomography/computed tomography showed minimal ¹⁸F-fluorodeoxyglucose (FDG) uptake in the pelvic mass but unexpectedly revealed FDG uptake throughout the skeleton, concerning for polyostotic fibrous dysplasia in the context of MAS. The adnexal mass was excised and pathology confirmed a JGCT. The patient’s affected bone and JGCT tissue revealed the same pathogenic GNAS p.R201C mutation, while her peripheral blood contained wild-type arginine at codon 201.

Conclusion

This mutation has been previously reported in cases of MAS and JGCT but never simultaneously in the same patient. This demonstration of a GNAS mutation underlying both JGCT and MAS in the same patient raises questions about appropriate surveillance for patients with these conditions.

Copy number alteration profiling facilitates differential diagnosis between ossifying fibroma and fibrous dysplasia of the jaws

Ossifying fibroma (OF) and fibrous dysplasia (FD) are two fibro-osseous lesions with overlapping clinicopathological features, making diagnosis challenging. In this study, we applied a whole-genome shallow sequencing approach to facilitate differential diagnosis via precise profiling of copy number alterations (CNAs) using minute amounts of DNA extracted from morphologically correlated microdissected tissue samples. Freshly frozen tissue specimens from OF (n = 29) and FD (n = 28) patients were obtained for analysis. Lesion fibrous tissues and surrounding normal tissues were obtained by laser capture microdissection (LCM), with ~30–50 cells (5 000–10 000 µm²) per sample. We found that the rate of recurrent CNAs in OF cases was much higher (44.8%, 13 of 29) than that in FD cases (3.6%, 1 of 28). Sixty-nine percent (9 of 13) of the CNA-containing OF cases involved segmental amplifications and deletions on Chrs 7 and 12. We also identified eight CNA-associated genes (HILPDA, CALD1, C1GALT1, MICALL2, PHF14, AIMP2, MDM2, and CDK4) with amplified expression, which was consistent with the copy number changes. We further confirmed a jaw lesion with a previous uncertain diagnosis due to its ambiguous morphological features and the absence of GNAS mutation as OF based on the typical Chr 12 amplification pattern in its CNA profile. Moreover, analysis of a set of longitudinal samples collected from an individual with a cellular lesion in suspicion of OF at the first surgery, recurrence and the latest malignant transformation revealed identical CNA patterns at the three time points, suggesting that copy number profiling can be used as an important tool to identify borderline lesions or lesions with malignant potential. Overall, CNA profiling of fibro-osseous lesions can greatly improve differential diagnosis between OF and FD and help predict disease progression.

Ossifying Fibroma of Non-odontogenic Origin: A Fibro-osseous Lesion in the Craniofacial Skeleton to be (Re-)considered

In the cranio-facial skeleton, a heterogeneous group of well characterized fibro-osseous lesions can be distinguished. Whereas fibrous dysplasia can affect any skeletal bone, ossifying fibroma and cemento-osseous dysplasia exclusively develop in the cranio-facial region, with most subtypes restricted to the tooth bearing areas of the jaws. Herein we present a series of 20 fibro-osseous lesions that developed mostly in the frontal bone and in the mandible, presenting as expansile intramedullary tumors with a unique histologic appearance and an indolent clinical course. We provide evidence that these tumors are distinct from the categories included in the WHO classification and are therefore currently unclassifiable. The definition of cemento-ossifying fibroma as an odontogenic neoplasm developing only in close proximity to teeth should be re-considered and incorporate also extragnathic lesions as shown here.

Soft Tissue Special Issue: Gnathic Fibro-Osseous Lesions and Osteosarcoma

Gnathic fibro-osseous lesions are a diverse group of disease processes which share overlapping microscopic features characterized by fibroblastic stroma with variable cellularity and a range of bone forming pathological processes leading to woven, sclerotic and cementum-like structures. Some of the lesions are unique to craniofacial location and a combination of clinical, radiological and pathological correlation is often necessary for diagnostic accuracy. Gnathic osteosarcomas are rare tumors with differences in age distribution and behavior as compared to osteosarcoma of long bones. This review will discuss the clinicopathological and radiological features of gnathic fibro-osseous lesions and osteosarcoma with updates on current genetics and molecular pathogenesis.

Molecular findings in maxillofacial bone tumours and its diagnostic value

According to the WHO, mesenchymal tumours of the maxillofacial bones are subdivided in benign and malignant maxillofacial bone and cartilage tumours, fibro-osseous and osteochondromatous lesions as well as giant cell lesions and bone cysts. The histology always needs to be evaluated considering also the clinical and radiological context which remains an important cornerstone in the classification of these lesions. Nevertheless, the diagnosis of maxillofacial bone tumours is often challenging for radiologists as well as pathologists, while an accurate diagnosis is essential for adequate clinical decision-making. The integration of new molecular markers in a multidisciplinary diagnostic approach may not only increase the diagnostic accuracy but potentially also identify new druggable targets for precision medicine. The current review provides an overview of the clinicopathological and molecular findings in maxillofacial bone tumours and discusses the diagnostic value of these genetic aberrations.

Benign fibro-osseous lesions of the jaws: a clinicopathologic study of 98 Tanzanian patients

Introduction: The benign fibro-osseous lesions (BFOL) are characterized by replacement of the normal bone by cellular fibrous tissue containing various forms of ossification. They encompass common clinical, radiologic and histopathological features and hence pose considerable diagnostic and therapeutic challenges to clinicians and pathologists. Objective: To analyze the clinico-pathological and radiological features of BFOLs of the jaws in patients treated at Muhimbili National Hospital, Tanzania. Material and methods: A retrospective study of files of patients who were diagnosed with BFOLs from January 2011 to December 2013 was done. The collected information included data on demographic characteristics, the duration of the lesion, location of the lesion, presence of swelling, associated symptoms and reported radiological and histological features. Results: A total of 98 patient's records were retrieved. There was a predominance of females (59, 60.2%), with a male to female ratio of 1:1.5. The patient's age at presentation ranged from 5 years to 75 years with a mean age of 29.81 ± 15.28 years. Four types of BFOLs were encountered. Ossifying fibroma were the most frequent (61.2%), followed by fibrous dysplasia (19.4%). Maxilla was more affected than the mandible. Majority (>70%) of the BFOLs were radio-opaque. The common histological features in all four types of BFOL included presence of: woven bone in fibrous stroma, giant cells, loose collagen and foci of hemorrhage. Conclusion: In this sample, BFOLs, were slightly more prevalent in females than males, affecting individuals below 40 years at large. They showed several overlapping clinical, radiological and histological features; thus a combination of different modalities seems necessary for an accurate diagnosis.

Next-Generation Sequencing in the Diagnosis of Rare Pediatric Sinonasal Tumors

The diagnosis of desmoid fibromatosis or other spindle cell tumors in the sinonasal region is very rare in children and needs to be thoroughly confirmed with immunohistochemical and/or molecular tests. We report 2 patients with such rare tumors and describe the use of next-generation sequencing in their evaluation. A 3-year-old female had a 4.4-cm midline nasal cavity mass involving the bony septum and extending into the base of the skull bilaterally. The moderate cellular fibroblastic proliferation revealed areas of thick keloid-like collagen bands and other areas with myxoid edematous stroma. Deep targeted sequencing identified a novel G34V mutation in the CTNNB1 gene consistent with desmoid fibromatosis. An 11-month-old male infant presented with a right nasal mass that extended through the cribriform plate into the anterior cranial fossa and involved the right ethmoid sinus and adjacent right orbit. Histology revealed an infiltrative atypical fibrous proliferation with focal calcifications that was negative for CTNNB1 and GNAS mutations. A novel RET E511K variant was identified in the tumor and later was also found in the germline and hence rendered of unknown significance. Both cases highlight the utility of next-generation sequencing in the evaluation of pediatric sinonasal spindle cell tumors that may have overlapping pathologic features. Reporting of rare or novel variants in tumor-only sequencing should be cautiously evaluated in children and pairing with germline sequencing may be needed to avoid the pitfall of assigning uncommon variants.

[The activating GNAS mutation : A survey of fibrous dysplasia, its associated syndromes, and other skeletal and extraskeletal lesions]

Fibrous dysplasia of bone is a connatal but not hereditary disease with monostotic or polyostotic manifestations and may be associated either with the extraskeletal disease McCune-Albright syndrome or with myxoma of the skeletal muscle, termed Mazabraud syndrome.The confirmation of recurrent chromosomal aberrations may lead to the conclusion that fibrous dysplasia is a neoplasia rather than a dysplastic skeletal disease.The primary cause of all forms of the described diseases is the activating GNAS mutation, which is detectable in almost all lesions. Research into the impact of this mutation has increased the understanding of these up to now solely descriptively defined diseases and also allowed easier discrimination of various fibro-osseous skeletal lesions. Current insights suggest that this mutation may also play a pivotal role in other extraskeletal neoplasias.

Multi-analytic study of a probable case of fibrous dysplasia (FD) from certosa monumental cemetery (Bologna, Italy)

OBJECTIVE

To evaluate, via a multidisciplinary approach, a distinctive paleopathological condition believed to be fibrous dysplasia, found on a 19th/20th century skeleton from Certosa Monumental Cemetery, Bologna, Italy.

MATERIALS

A skeletonized cranium and mandible recovered from an ossuary in 2014.

METHODS

Pathological alterations were analysed by radiological examination, dental macrowear, histopathological and genetic analyses.

RESULT

The skeleton is believed to be an adult male. Differential diagnoses include Paget's disease, McCune-Albright syndrome, osteochondroma and osteosarcoma. The radiographic findings, along with the solitary nature of the lesions, are strong evidence for the diagnosis of fibrous dysplasia (FD). Genetic analysis further revealed a frequency of ˜1% of mutant alleles with the R201C substitution, one of the post-zygotic activating mutation frequently associated with FD.

CONCLUSIONS

The multi-analytical method employed suggests a diagnosis of monostotic form of FD. The diagnostic design incorporates multiple lines of evidence, including macroscopic, histopathological, and genetic analyses.

SIGNIFICANCE

Through the use of a multi-analytic approach, robust diagnoses can be offered. This case serves as one of the oldest examples of FD from an historical context. The genetic mutation detected, associated with FD, has not been previously reported in historical/ancient samples.

Fibrous dysplasia of the jaws: Integrating molecular pathogenesis with clinical, radiological, and histopathological features

Fibrous dysplasia is a non-neoplastic developmental process that affects the craniofacial bones, characterized by painless enlargement as a result of bone substitution by abnormal fibrous tissue. Postzygotic somatic activating mutations in the GNAS1 gene cause fibrous dysplasia and have been extensively investigated, as well as being helpful in the differential diagnosis of the disease. Fibrous dysplasia may involve one (monostotic) or multiple bones (polyostotic), sporadically or in association with McCune-Albright syndrome, Jeffe-Lichenstein syndrome, or Mazabreud syndrome. This review summarizes the current knowledge on fibrous dysplasia, emphasizing the value of integrating the understanding of its molecular pathogenesis with the clinical, radiological, and histopathological features. In addition, we address important aspects related to the differential diagnosis and patient management.

HDAC8, A Potential Therapeutic Target, Regulates Proliferation and Differentiation of Bone Marrow Stromal Cells in Fibrous Dysplasia

Fibrous dysplasia (FD) is a disease of postnatal skeletal stem cells caused by activating mutations of guanine nucleotide-binding protein alpha-stimulating activity polypeptide (GNAS). FD is characterized by high proliferation and osteogenesis disorder of bone marrow stromal cells (BMSCs), resulting in bone pain, deformities, and fractures. The cAMP-CREB pathway, which is activated by GNAS mutations, is known to be closely associated with the occurrence of FD. However, so far there is no available targeted therapeutic strategy for FD, as a critical issue that remains largely unknown is how this pathway is involved in FD. Our previous study revealed that histone deacetylase 8 (HDAC8) inhibited the osteogenic differentiation of BMSCs via epigenetic regulation. Here, compared with normal BMSCs, FD BMSCs exhibited significantly high proliferation and weak osteogenic capacity in response to HDAC8 upregulation and tumor protein 53 (TP53) downregulation. Moreover, inhibition of cAMP reduced HDAC8 expression, increased TP53 expression and resulted in the improvement of FD phenotype. Importantly, HDAC8 inhibition prevented cAMP-induced cell phenotype and promoted osteogenesis in nude mice that were implanted with FD BMSCs. Mechanistically, HDAC8 was identified as a transcriptional target gene of CREB1 and its transcription was directly activated by CREB1 in FD BMSCs. In summary, our study reveals that HDAC8 associates with FD phenotype and demonstrates the mechanisms regulated by cAMP-CREB1-HDAC8 pathway. These results provide insights into the molecular regulation of FD pathogenesis, and offer novel clues that small molecule inhibitors targeting HDAC8 are promising clinical treatment for FD. Stem Cells Translational Medicine 2019;8:148&14.

Fibrous dysplasia imitating malignancy

Fibrous dysplasia is a benign bone disease, presenting as monostotic or polyostotic lesions, or as part of a syndrome (McCune-Albright/Mazabraud). Its clinical course shows a variegated picture and the progression of its growth is unpredictable. In the workup of 39 fibrous dysplasia cases in the cranio-facial area, four cases presented fast growth tendencies, of which two patients with McCune-Albright syndrome showed malignant-like rapid growth. This local aggressive form is extremely rare, and the concept of this issue has not been clearly defined. With regard to the speed of growth a volumetric-time analysis in one of our cases demonstrated a 74 days tumor doubling rate with an exponential growth curve. According to the literature the aggressive form presented extra-cranially mainly at an adult age, whereas its appearance in our cranio-facial patient collective was much younger. Distinguishing nonmalignant and malignant aggressive forms is difficult and highly inconsistent in the literature. We therefore implemented a quantitative growth measure analysis to define aggressive forms based on progression and speed of growth and impartial of type of FD, localization or functional incapacity. Due to our study findings and literature review we state a prevalence of an aggressive form might be possibly about 5 %.

The curious case of Gαs gain-of-function in neoplasia

BACKGROUND

Mutations activating the α subunit of heterotrimeric Gs protein are associated with a number of highly specific pathological molecular phenotypes. One of the best characterized is the McCune Albright syndrome. The disease presents with an increased incidence of neoplasias in specific tissues.

MAIN BODY

A similar repertoire of neoplasms can develop whether mutations occur spontaneously in somatic tissues during fetal development or after birth. Glands are the most "permissive" tissues, recently found to include the entire gastrointestinal tract. High frequency of activating Gαs mutations is associated with precise diagnoses (e.g., IPMN, Pyloric gland adenoma, pituitary toxic adenoma). Typically, most neoplastic lesions, from thyroid to pancreas, remain well differentiated but may be a precursor to aggressive cancer.

CONCLUSIONS

Here we propose the possibility that gain-of-function mutations of Gαs interfere with signals in the microenvironment of permissive tissues and lead to a transversal neoplastic phenotype.

Conservative Management of Central Cemento-Ossifying Fibroma

Central cemento-ossifying fibroma is characterized by the combined production of osteoid and cementoid tissue. Radiographically, this lesion is presented as an outlined cortical and variable radiopaque spots, also can be present complete radiolucent or different degrees of radiopacity. The recommended treatment is curettage or enucleation, and the recurrence rate is less than 5%. Considering that surgical treatment is invasive, mainly in large lesions, this study aims to report a patient in whom conservative treatment was carried out by involving the preservation of teeth, with a long-term follow-up. A 48-year-old black female patient, diagnosed with central cemento-ossifying fibroma in mandible, treated conservatively and a 2 years of follow-up. It was concluded that the conservative treatment with a long term of follow-up for maintaining teeth was satisfactory.

Frequency of GNAS R201H substitution mutation in polyostotic fibrous dysplasia: Pyrosequencing analysis in tissue samples with or without decalcification

Guanine nucleotide-binding protein/α-subunit (GNAS) mutations are involved in fibrous dysplasia (FD) pathogenesis. Here, we analyzed GNAS mutations in FD which were performed by pyrosequencing DNA isolated from formalin-fixed paraffin-embedded (FFPE) tissue. The mutation detection rate was determined in FD specimens with and without decalcification. GNAS mutation was identified in 28 cases out of 87 FDs (32.18%) [p.R201C (N = 14) and p.R201H (N = 14)]. GNAS mutation was more likely to occur in polyostotic FD (7/28, 25.0%); FD without GNAS mutation was mostly monostotic form (56/59, 94.9%, P = 0.011). The G > A (R201H) mutation was more frequent in polyostotic FD (6/14 patients, 42.9%) than the C > T (R201C) mutation (1/14, 7.1%) (P = 0.077). We divided the FD cases into two subgroups: tissue specimens that were not decalcified (N = 35, 40.2%), and tissue specimens that were decalcified (N = 52, 59.8%). GNAS mutation was more frequently identified in FD specimens that were not subjected to decalcification (23/35, 65.7%) than in FD specimens that were decalcified (5/52, 9.6%) (P = 0.001). In conclusion, mutation analysis of GNAS by pyrosequencing has diagnostic value in FFPE tissue of patients with FD, especially in specimens that were not decalcified. The R201H substitution mutation of GNAS may be involved in the pathogenesis of polyostotic FD.

Imaging of the Central Skull Base

The skull base is a complex bony and soft tissue interface that is divided anatomically into compartments. This article will focus specifically on the central skull base, which has a complex embryologic development and anatomy. Multiple entities from notochord remnants, neoplasm, infection, and other abnormalities may occur, and imaging is critical for depicting skull base pathology.

CDC73 gene mutations in sporadic ossifying fibroma of the jaws

Background

The tumor suppressor gene CDC73 was found to be associated with hyperparathyroidism-jaw tumor syndrome (HPT-JT), which is characterized by parathyroid adenoma or carcinoma, ossifying fibroma (OF) of the jaws, and renal and uterine lesions. Mutations in CDC73 have also been frequently detected in sporadic parathyroid carcinomas and renal tumors. However, the prevalence and range of CDC73 mutations in sporadic OFs have not been established.

Methods

We directly sequenced coding and flanking splice junctional regions of CDC73 in 40 cases of sporadic OF of the jaws. We also used immunohistochemistry to detect parafibromin, the protein product of CDC73, in those cases.

Results

Two novel CDC73 mutations were identified in 2 of the 40 cases (5 %). Both were somatic mutations located in exon 1 of the coding region. Strong parafibromin expression was detected in all 40 cases, irrespective of the presence of CDC73 mutations.

Conclusions

Mutations inCDC73 were rare in sporadic OF of the jaws, but may affect the pathogenesis of a small subset of tumors of this type.

Clinicopathological implications of GNAS in Ewing sarcoma

The objective of the present study was to determine whether guanine nucleotide-binding protein α stimulating (GNAS) gene expression correlates with pathognomonic signs by analyzing the mutations, methylation status and G-protein α subunit (G_sα) expression of GNAS in Ewing sarcoma (ES). Formalin-fixed paraffin-embedded tissue samples from 77 patients with primary ES were obtained in South Korea, Argentina and Brazil, and were studied via methylation chip assay and direct sequencing of the GNAS gene and immunohistochemical analysis of G_sα. The mutation and methylation statuses of the GNAS gene were examined. Immunohistochemical results were measured with respect to proportion and staining intensity. The results revealed that GNAS genes in ES tumor samples were less methylated compared with normal controls. No mutations were detected at exons 8 or 9 of the GNAS locus complex on chromosome 20q13.3, indicating that the pathogenesis of ES was not associated with GNAS mutation. G_sα expression correlated well with the methylation status of the GNAS gene. Notably, high G_sα expression was detected more frequently in samples from living patients than from decedents, although this was not statistically significant (P=0.055). In conclusion, GNAS mutation is not associated with the pathogenesis of ES tumors. This finding may be used to differentiate ES tumors from metastatic bone lesions with morphological similarity to ES tumors. Analysis of the methylation status of the GNAS gene and immunohistochemical G_sα expression suggests that hypermethylated GNAS (low G_sα expression) in ES may be associated with unfavorable progression with a non-significant trend.

Central Cemento-Ossifying Fibroma: Primary Odontogenic or Osseous Neoplasm?

Currently, central cemento-ossifying fibroma is classified by the World Health Organization as a primary bone-forming tumor of the jaws. However, histopathologically, it is often indistinguishable from cemento-osseous dysplasias in that it forms osteoid and cementicles (cementum droplets) in varying proportions. It is believed that pluripotent cells within the periodontal membrane can be stimulated to produce either osteoid or woven bone and cementicles when stimulated. If this is true, cemento-ossifying fibroma would be better classified as a primary odontogenic neoplasm arising from the periodontal ligament. Cemento-ossifying fibromas also do not occur in the long bones. The present report compares several entities that fall within the diagnostic realm of benign fibro-osseous lesions and reviews the evidence for reclassifying central cemento-ossifying fibroma as a primary odontogenic neoplasm.

GNAS mutations are not detected in parosteal and low-grade central osteosarcomas

Parosteal osteosarcoma, low-grade central osteosarcoma, and fibrous dysplasia share similar histological features that may pose a diagnostic challenge. The detection of GNAS mutations in primary bone tumors has been useful in clinical practice for diagnosing fibrous dysplasia. However, the recent report of GNAS mutations being detected in a significant proportion of parosteal osteosarcoma challenges the specificity of this mutation. As the number of cases reported in this study was small we set out to determine if these results could be reproduced. We studied 97 formalin-fixed paraffin-embedded low-grade osteosarcomas from 90 patients including 62 parosteal osteosarcomas, of which MDM2 amplification was detected in 79%, 11 periosteal osteosarcomas and 24 low-grade central osteosarcoma samples. The mutational status of GNAS was analyzed in codons p.R201, p.Q227, and other less common GNAS alterations by bidirectional Sanger sequencing and/or next generation sequencing using the Life Technologies Ion Torrent platform. GNAS mutations were not detected in any of the low-grade osteosarcomas from which informative DNA was extracted. Our findings therefore support prior observations that GNAS mutations are highly specific for fibrous dysplasia and occur rarely, if ever, in parosteal and other low-grade osteosarcomas.

Chromosome 12 long arm rearrangement covering MDM2 and RASAL1 is associated with aggressive craniofacial juvenile ossifying fibroma and extracranial psammomatoid fibro-osseous lesions

To evaluate the diagnostic value of MDM2 status in craniofacial fibro-osseous lesions, we investigated MDM2 expression by immunohistochemistry and analyzed MDM2 amplification by qPCR in 30 cases of ossifying fibroma (including 13 cases of the juvenile variant) and 17 cases of fibrous dysplasia. Two cases of uncommon extragnathic psammomatoid fibrous dysplasia and a mixed control group of 15 cases of low-grade osteosarcoma and 15 cases of well-differentiated/dedifferentiated liposarcoma were included. MDM2 amplification was found in 33% of ossifying fibromas (peak of 69% for the juvenile variant) and in 12% of fibrous dysplasia, in none of which was MDM2 overexpressed. All control cases exhibited MDM2 amplification and overexpression. To investigate possible polysomy of chromosome 12, we studied RASAL1 amplification, a gene telomeric to MDM2 on the long arm of chromosome 12. RASAL1 amplification was reported in all benign fibro-osseous lesions exhibiting MDM2 amplification but not in controls. Simultaneous amplification of these two genes was significantly higher in juvenile ossifying fibromas compared with fibrous dysplasia (P=0.004), non-juvenile ossifying fibromas (P=0.001), and all other benign craniofacial fibro-osseous lesions combined (P=0.0001). Of the nine cases of juvenile ossifying fibroma exhibiting amplification, three were locally invasive and four were recurrent, suggesting aggressive disease. The two cases of extragnathic psammomatoid fibrous dysplasia also showed MDM2 and RASAL1 amplification with no MDM2 overexpression. This large chromosome 12 rearrangement, spanning MDM2 and RASAL1, is the first recurrent molecular abnormality to be reported in juvenile ossifying fibroma. It may represent both a molecular diagnostic marker and a characteristic of more aggressive forms with a higher risk of recurrence. Finally, the presence of this rearrangement in extragnathic psammomatoid fibro-osseous lesions mimicking ossifying fibromas might reflect a common molecular pathway in their pathogenesis and calls into question the classification of such lesions within fibrous dysplasia.

Maxillofacial fibro-osseous lesions

During the last decade much has changed in our understanding of fibro-osseous lesions (FOLs) of the jaws with regards to their imaging, their nomenclature and classification, and their potential impact on the overall health of the patient. The changes in nomenclature, classification, and the FOLs' potential association with important syndromes are discussed with the assistance of a flowchart. The lesions, fibrous dysplasia (FD), ossifying fibroma (OF), and osseous dysplasia (OD), though with similar histopathology, have very different clinical and radiological presentations, behaviour, and treatment outcomes. FD of the jaw, which though becoming inactive, does not involute and therefore requires life-long review to monitor for occasional reactivation. OF is completely removed surgically as it has a propensity to recur. No treatment is generally required for an OD unless it is infected or displays expansion. Lesions outside the jaws associated with FOLs of the jaws are identified. Radiology remains central to the diagnosis of FOLs of the jaw, because the pathologist is still not able to distinguish between them. The advent of cone-beam computed tomography (CBCT) with its better radiation dose reduction, accessibility, and spatial resolution has transformed imaging of FOLs. Their presentations on CBCT and the clinical indications for its use are discussed.

Desmoplastic fibroma of the rib with cystic change: a case report and literature review

Desmoplastic fibroma (DF) is a rare, locally aggressive, solitary tumor microscopically composed of well-differentiated myofibroblasts with abundant dense collagen deposition. The most common sites are the long tubular bones and mandible. To our knowledge, only five cases of DF in the ribs have been reported. Here, we report a case of DF in this rare location with unusual radiological findings. A 40-year-old man presented with a 4-year history of swelling of the right chest wall. Radiographs revealed a mass at the right 9th rib, and computed tomography demonstrated a mass of 14 × 12 × 8 cm at the right 9th rib with expanded cystic change and marked calcification that appeared to have arisen from the bone. Open biopsy suggested DF. Total excision was performed, and the chest wall was reconstructed. The surgical specimen was a yellowish tumor with multilocular cystic change containing a viscous liquid. The tumor was composed of a proliferation of less-atypical spindle-shaped cells in a collagenous background. The cystic change was observed in the extra-osseous lesion. No β-catenin cytoplasmic/nuclear accumulation was detected, and no β-catenin or GNAS genetic mutations were detected. A final diagnosis of DF was made on the basis of the pathological and radiological findings. The patient was successfully treated with total excision of the tumor with no evidence of recurrence 6 months after surgery.

Two cases of multiple ossifying fibromas in the jaws

BACKGROUND

The clinicopathologic characteristics of multiple ossifying fibroma (OF) are unclear due to the condition's rarity, making diagnosis challenging. Sporadic multiple OFs must be distinguished from hyperparathyroidism-jaw tumour syndrome (HPT-JT) related OF and other fibro-osseous lesions.

METHODS

Multiple OF cases were identified from ossifying fibroma cases. Clinical data including age, sex, anatomic site, radiographic features, clinical impression, treatment and available follow-up data as well as serum calcium, phosphorus, and parathyroid hormone (PTH) were recorded. GNAS and HRPT2 genetic mutations were examined in the two present cases. Case reports of sporadic multiple ossifying fibroma and HPT-JT-related OF were also reviewed.

RESULTS

The two present cases were confirmed as sporadic multiple OF, with no genetic GNAS and HRPT2 mutations found. The incidence of sporadic multiple ossifying fibroma was 2.0% (2/102). The total 18 sporadic multiform OF cases were characterized as followed: 13 (72.2%) female; 5 (27.8%) male; mean age 28.6 years; 2/16 (11.1%) cases only in the mandible; 4/18 (22.2%) cases only in the maxilla; and 12/18 (66.7%) cases in both the maxilla and mandible. Radiographically, the lesions were radiolucent in 5/18 (27.8%) cases and mixed density in 13/18 (72.2%) cases. Along with 24 cases of HPT-JT related OF were reviewed, sixteen (66.7%) patients were diagnosed with a single lesion, and 8 patients (33.3%) were diagnosed with multiple jaw lesions.

CONCLUSIONS

Sporadic multiple OFs are very rare, but must be distinguished from HPT-JT related OF. We strongly recommend that patients diagnosed with multiple ossifying fibromas receive serum PTH testing and mutation screening of HRPT2.

VIRTUAL SLIDES

http://www.diagnosticpathology.diagnomx.eu/vs/1194507146115753.