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

Giant Cell-Rich Tumors of the Skeleton

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

Striated Duct Adenoma: A Case Report and a Scoping Review

INTRODUCTION

Striated duct adenoma (SDA) is a rare benign salivary gland tumor with a recently described genetic signature. Recurrent oncogenic mutations affecting the IDH2 gene differentiate SDA from its primary differential diagnosis of canalicular adenoma. Here, we report a case of SDA affecting the parotid gland with IDH1/2 mutation-specific immunohistochemical positivity. Additionally, we provide a scoping review developed according to the Cochrane Methodology and reported following the Joana Briggs Institute (JBI) checklist to synthesize all previously published cases of SDA. The review protocol was registered on the Open Science Framework (OSF) platform ( https://osf.io/7mztg ). The searches were performed using Medline, Embase, Web of Science, and LILACS, with no date or language limit. Studies were evaluated for eligibility, extracted, and compiled in a narrative form. Seven studies with 20 patients with SDA, including ours, were analyzed. The tumors mainly affected the parotid gland (13/20) in patients with a mean age of 62 years and did not display sex predilection. Swelling was the leading clinical symptom. The mean follow-up duration was 26 months with no recurrence or metastasis after resection.

CONCLUSION

Awareness of the clinicopathological features and the use of IDH1/2 mutation-specific immunohistochemistry are pivotal for the consistent identification of SDA, and assessment for true biological potential will require increased follow-up and scrutiny.

Tenosynovial giant cell tumor: case report and molecular investigation

Tenosynovial giant cell tumor is a benign neoplasm arising from the synovium of joints, including the temporomandibular joint (TMJ). Despite its benign nature, these tumors may exhibit aggressive behavior. A 57-year-old woman with a swollen, hardened area in the left TMJ was referred to the university´s clinic. The diagnosis of tenosynovial giant cell tumor was made based on the presence of hyperplastic synovial lining containing mononuclear and giant cells, hemorrhagic areas, hemosiderin deposits, and calcification foci in the biopsy. A low condylectomy was performed, and histopathologic analysis of the surgical piece upheld the diagnosis. Due to histopathologic resemblance with other giant cell-rich lesions (giant cell granuloma of the jaws, brown tumor of hyperparathyroidism, and non-ossifying fibroma) for which signature mutations are known, mutational analysis of KRAS, FGFR1, and TRPV4 genes was conducted. The results revealed wild-type sequences for all the mutations tested, thereby supporting the diagnosis of tenosynovial giant cell tumor.

Multiple central giant cell granuloma of the jaws: diagnostic signposts of Noonan syndrome and RASopathy

Noonan syndrome (NS) is a phenotypically variable inherited multi-system disorder. Maxillofacial findings can be diagnostic, especially in the evaluation of discrete facial dysmorphia. Diagnostic landmark findings of therapeutic relevance for the jaws such as central giant cell granuloma (CGCG) are rare in NS. However, recent molecular genetic studies indicate that these rare, benign lesions are neoplasms and more common in specific syndromes grouped under the umbrella term RASopathies. A specialist surgical diagnosis can be helpful in identifying the underlying disease. This report outlines diagnosis and treatment of a case of CGCG for which jaw diagnosis became the key to identifying a syndromic disease.

Imaging of Fibro-osseous Lesions and Other Bone Conditions of the Jaws

This review directs the focus on the imaging features of various fibro-osseous lesions and other bone lesions that can be of similar presentation. Broad diagnosis of "fibrous osseous lesion" may culminate in improper treatment and management. Radiographic discriminating factors between these entities are highlighted and summarized to improve the diagnostic process when encountering these lesions.

An Audit of Histopathological Pattern of Peripheral Giant Cell Granuloma - A Retrospective Study

Introduction

Peripheral giant cell granuloma (PGCG) is a type of reactive hyperplastic lesion in the oral cavity that develops due to local irritation or chronic trauma, originating from the periosteum or periodontal membrane. It primarily affects the alveolar mucosa of the posterior mandibular region and has a peak incidence in the age range of the fourth to sixth decades of life, with a 2:1 female predilection. The aim of the study was to analyse the histopathological pattern of peripheral giant cell granuloma.

Materials and Methods

This retrospective study was conducted at a tertiary care teaching hospital from 2018 to 2023 after obtaining the required institutional ethical board approval (SMC/UECM/2023/627/296). All the cases of maxillofacial lesions referred/reported to and which conformed to the set inclusion and exclusion criteria were included. Data were analysed by calculating the percentage of the variables. IBM SPSS version 20 software was used to analyse the descriptive data.

Results

Out of 12 patients, four were males and eight were females. The age ranged from 20 to 60 years with an average age of 40 years. All the patients included in the study showed multinucleated giant cells and inflammatory cells, 83.3% showed fibrous stroma and 50% showed para-keratinisation and haemosiderin pigments.

Discussion

PGCG, a reparative lesion, seems to occur mostly in the 40-60 years of life with female predilection and commonly seen histopathological features included multinuclear giant cells, inflammatory cells in all cases, 83.3% fibrous stroma and 50% both para-keratinisation and haemosiderin pigments.

DNA methylation profile discriminates sporadic giant cell granulomas of the jaws and cherubism from their giant cell-rich histological mimics

Sporadic giant cell granulomas (GCGs) of the jaws and cherubism-associated giant cell lesions share histopathological features and microscopic diagnosis alone can be challenging. Additionally, GCG can morphologically closely resemble other giant cell-rich lesions, including non-ossifying fibroma (NOF), aneurysmal bone cyst (ABC), giant cell tumour of bone (GCTB), and chondroblastoma. The epigenetic basis of these giant cell-rich tumours is unclear and DNA methylation profiling has been shown to be clinically useful for the diagnosis of other tumour types. Therefore, we aimed to assess the DNA methylation profile of central and peripheral sporadic GCG and cherubism to test whether DNA methylation patterns can help to distinguish them. Additionally, we compared the DNA methylation profile of these lesions with those of other giant cell-rich mimics to investigate if the microscopic similarities extend to the epigenetic level. DNA methylation analysis was performed for central (n = 10) and peripheral (n = 10) GCG, cherubism (n = 6), NOF (n = 10), ABC (n = 16), GCTB (n = 9), and chondroblastoma (n = 10) using the Infinium Human Methylation EPIC Chip. Central and peripheral sporadic GCG and cherubism share a related DNA methylation pattern, with those of peripheral GCG and cherubism appearing slightly distinct, while central GCG shows overlap with both of the former. NOF, ABC, GCTB, and chondroblastoma, on the other hand, have distinct methylation patterns. The global and enhancer-associated CpG DNA methylation values showed a similar distribution pattern among central and peripheral GCG and cherubism, with cherubism showing the lowest and peripheral GCG having the highest median values. By contrast, promoter regions showed a different methylation distribution pattern, with cherubism showing the highest median values. In conclusion, DNA methylation profiling is currently not capable of clearly distinguishing sporadic and cherubism-associated giant cell lesions. Conversely, it could discriminate sporadic GCG of the jaws from their giant cell-rich mimics (NOF, ABC, GCTB, and chondroblastoma).

Response of Central Giant Cell Granuloma of the Jaw to Imatinib

Central giant cell granuloma of the jaw (CGCJ) can be locally aggressive and result in facial and dental deformity. A child with CGCJ was treated surgically and with denosumab with a response but life-threatening toxicity. Imatinib, a tyrosine kinase inhibitor, was prescribed based on clinical similarities between CGCJ and cherubism, for which Imatinib has been effective. Within 2 months, a computed tomographic scan showed significant ossification, which increased over the following 8 months. This case suggests that tyrosine kinase inhibitors may be an effective option, and one with limited toxicity, for CGCJ.

Aggressive giant cell lesion of mandible-confusing to common: true neoplasm versus reactive lesion

Destructive lesions in the craniofacial region especially in the jawbones, if associated with giant cells, include a spectrum of lesions that pose difficulty in diagnosis. The nature of such a lesion in the jawbones is questionable about whether it is a reactive/benign lesion or aggressive/non-aggressive. Clinical, radiological and histopathological correlation may be a reliable indicator to differentiate between the qualities of the lesion, which directly accounts for effective and individual planning of the treatment. Here we present a case of a woman in her late 20s with an unusual destructive lesion of the mandible.

A new TRPV4 mutation in a case of multiple central giant cell granulomas of the jaws

Sporadic central giant cell granulomas of the jaws (GCGJ) are often solitary lesions, characterized by KRAS, FGFR1, and TRPV4 somatic mutations. Multifocal lesions may occur and are associated with hyperparathyroidism or underlying syndromes such as cherubism, which is marked by SH3BP2 mutations, and RASopathies, which are caused by mutations in the FGFR-RAS-RAF-MEK-ERK signaling cascade. The diagnosis of multiple GCGJ can be challenging. The present case reports a 14-year-old boy with multiple central GCGJ and no obvious syndromic trait. Sanger sequencing-based analysis revealed wild-type sequences for SH3BP2 (exon 9), KRAS (exons 2-4), and FGFR1 (exons 9 and 10) genes. A rare TRPV4 somatic mutation (p.Val708Met) was detected in the lesion on the right side of the mandible, whereas the other tumor and the normal oral mucosa revealed wild-type TRPV4 sequences. This report expands the spectrum of TRPV4 somatic mutations in central GCGJ.

Oral giant cell tumor or giant cell granuloma: How to know?

Introduction

The distinction between giant cell tumors and giant cell granulomas is challenging, as both entities have overlapping diagnostic criteria, especially in oral locations. The two entities have similar clinical and radiological presentations, but they differ in their prognoses.

Objective

The main objective of this study was to list the clinical, radiological, histological, and prognostic features of maxillomandibular giant cell tumors and giant cell granulomas cases n order to assess their value as a diagnostic referral factor that may allow the distinction between maxillo-mandibular giant cell granuloma and giant cell tumor.

Study design

Data of maxillomandibular giant cell granulomas and giant cell tumors were assessed through a scoping review and a pre-existing systematic review of literature. We have also realized a bicentric retrospective study.

Results

Various criteria facilitate the differential diagnosis like age, size, locularity and presence of necrosis zone but not the gender. The most discriminating factors was symptomatology (reported in 72% of GCTs while only 15% of GCGs) and the distribution pattern of giant cells in the stroma (homogeneously dispersed in 80% of GCTs versus grouped in clusters in 86.7% of GCGs). Recurrences were most described for giant cell tumors than giant cell granulomas. Malignant transformation and pulmonary metastasis were exclusively reported for giant cell tumors.

Conclusion

As clinical and radiological elements are not sufficient to distinguish between these two entities, immunohistochemistry and molecular genetics can be represent diagnostic biomarkers to distinguish giant cell granulomas and giant cell tumors in oral cavity. We have attempted to define the main criteria for the differentiation of giant cell tumor and giant cell granuloma and propose a decision tree for the management of single maxillomandibular giant cell lesions.

Integrated proteomics, phosphoproteomics and metabolomics analyses reveal similarities amongst giant cell granulomas of the jaws with different genetic mutations

BACKGROUND

Giant cell granuloma of the jaws are benign osteolytic lesions of the jaws. These lesions are genetically characterized by mutually exclusive somatic mutations at TRPV4, KRAS, and FGFR1, and a fourth molecular subgroup which is wild-type for the three mutations. Irrespective of the molecular background, giant cell granulomas show MAPK/ERK activation. However, it remains unclear if these mutations lead to differences in their molecular signaling in giant cell granulomas.

METHODS

Metabolomics, proteomics and phosphoproteomics analyses were carried out in formalin-fixed paraffin-embedded samples of giant cell granuloma of the jaws. The study cohort consisted of five lesions harboring mutations in FGFR1, six in KRAS, five in TRPV4 and five that were wild-type for these mutations.

RESULTS

Lesions harboring KRAS or FGFR1 mutations showed overall similar proteomics and metabolomics profiles. In all four groups, metabolic pathways showed similarity in apoptosis, cell signaling, gene expression, cell differentiation and erythrocyte activity. Lesions harboring TRPV4 mutations showed a greater number of enriched pathways related to tissue architecture. On the other hand, the wild-type group presented increased number of enriched pathways related to protein metabolism compared to the other groups.

CONCLUSION

Despite some minor differences, our results revealed an overall similar molecular profile among the groups with different mutational profile at the metabolic, proteic and phosphopeptidic levels. This article is protected by copyright. All rights reserved.

Manifestations of hyperparathyroidism in the jaws: Concepts, mechanisms, and clinical aspects

Hyperparathyroidism is one of the most common endocrine disorders worldwide. In countries where routine biochemical screening is not common, symptomatic hyperparathyroidism predominates. Its manifestations include skeletal alterations, calcification of soft tissues, kidney stones, and functional alterations in other systems. Notably, jaw alterations can be the first clinical sign of hyperparathyroidism, including brown tumor, renal osteodystrophy, osteitis fibrosa, and leontiasis ossea, and knowing such conditions is of core importance for the multidisciplinary diagnosis and management of hyperparathyroidism. We aimed to perform a concise review, systematizing the concepts and mechanisms underlying hyperparathyroidism and associated gnathic alterations. In addition, a detailed description of the clinical aspects of the jaw manifestations is presented.

Update from the 5th Edition of the World Health Organization Classification of Head and Neck Tumors: Odontogenic and Maxillofacial Bone Tumours

The 5^th edition of the World Health Organization (WHO) Classification of Head and Neck Tumours (2022) comes out only five years after the previous edition, however it presents important updates that run in parallel with the rapid progression involving the increasingly sophisticated molecular investigation and its interpretation, some of which already have therapy-related impact. This manuscript provides an overview of the leading changes introduced in the classification of Odontogenic and Maxillofacial Bone Tumours that encompasses cysts of the jaws, odontogenic tumours, giant cell lesions and bone cysts, and bone and cartilage tumours. This is the first edition that Essential and Desirable Diagnostic Features were added for each entity, so that the most important clinical, microscopic and/or radiologic features were encapsulated and briefly highlighted. Surgical ciliated cyst was added to the group of odontogenic cysts, adenoid ameloblastoma was a newly recognized benign epithelial odontogenic tumour, and segmental odontomaxillary dysplasia was introduced in the group of fibro-osseous tumours and dysplasia. In addition, rhabdomyosarcoma with TFCP2 rearrangement, was introduced into the group of malignant jawbone tumours. The unique genetic aberrations distinguish it from other types of rhabdomyosarcomas. On the other hand, melanotic neuroectodermal tumour of infancy and osteoid osteoma were deleted from the benign bone and cartilageneous tumours, as was the hematolymphoid tumour of solitary plasmacytoma of bone. We systematically reviewed each entity in this chapter and provided important updated findings for selected topics that can further aid in the diagnostic process for challenging cases, broaden insights on the logic of the present classification, and finally, emphasize the potential that some of the molecular results may have in the near future to set new treatment approaches.

Central giant cell granuloma of the mandibular condyle: additional case and literature review

Introduction: Central giant cell granuloma (CGCG) of the jaws is not a common lesion. Only five cases are reported in the mandibular condyle. Observation: A 25 year-old male presented with preauricular swelling and a premature occlusal contact on the molars. The lesion had radiological features of aggressiveness and a high metabolic uptake. Initial biopsy was misleading. The lesion was treated surgically by resection. Discussion: Histologically, CGCG are very similar to other giant cell lesions such as GCT (Giant cell Tumor) or BTH (brown tumor of hyperparathyroidism). The standard treatment is surgical either by curettage or resection. Only 6 cases have been described in the literature, including this one. The diagnosis is difficult, relying on a bundle of clinical, radiological and histological arguments. However, radical surgery should be performed to avoid the tumor recurrence. The genetic mutations associated with CGCG (notably TRPV4 and RAS pathway) may explain why this tumor is mostly found in the dental part of the jaws and only rarely in the mandibular condyle.

Neurofibromatosis Type 1 With Cherubism-like Phenotype, Multiple Osteolytic Bone Lesions of Lower Extremities, and Alagille-syndrome: Case Report With Literature Survey

BACKGROUND/AIM

Neurofibromatosis type 1 (NF) is an autosomal dominant hereditary disease. The cardinal clinical findings include characteristic skeletal alterations. Difficulties in diagnosis and therapy can arise if an individual has further illnesses.

CASE REPORT

This is a case report of a 16-year-old patient affected by NF1. She also suffered from Alagille syndrome and the consequences of fetal alcohol exposure. The patient's facial phenotype showed findings that could be assigned to one or more of the known diseases. The patient was referred for treating a cherubism-like recurrent central giant cell granuloma (CGCG) of the jaw. The patient developed bilateral, multilocular non-ossifying fibromas (NOF) of the long bones of the lower extremity. Treatment of the skeletal lesions consisted of local curettage. While NOF regressed after surgery, the CGCG of the jaw remained largely unchanged. Extensive genetic tests confirmed a previously unknown germline mutation in the JAG1 gene, the germline mutation of the NF1 gene, and the somatic mutation in the NF1 gene in the diffuse plexiform neurofibroma, but not in the CGCG.

CONCLUSION

Assigning facial findings to a defined syndrome is ambiguous in many cases and especially difficult in patients who have multiple diseases that can affect the facial phenotype. Surgical therapy should be adapted to the individual findings.

KRAS Mutation in an Implant-associated Peripheral Giant Cell Granuloma of the Jaw: Implications of Genetic Analysis of the Lesion for Treatment Concept and Surveillance

The aim of this case report was to detail diagnosis and therapy in a case of implant-associated peripheral giant cell granuloma (IA-PGCG) of the jaw. Case Report: The 41-year-old female attended the outpatient clinic for treatment of recurrent mandibular IA-PGCG. The lesion was excised and the defect was closed with a connective tissue graft of the palate. Healing of oral defects was uneventful, and no local recurrence has occurred during a follow-up of 7 months. Genetic examination of the lesion identified a somatic mutation in KRAS. Conclusion: The lesions are assessed as reactive-inflammatory changes in the mucous membrane of the oral cavity. The cause of the lesion is unknown. KRAS mutations are commonly found in various cancer tissues, but also in germline and mosaic RASopathies. Recently, KRAS mutations have been identified in several IA-PGCG. The clinical course of a frequently locally recurring lesion gives rise to the assumption that lesions of this type show characteristics known in benign neoplasms.

Towards better understanding of giant cell granulomas of the oral cavity

Giant cell granulomas are enigmatic lesions of the oral cavity characterised by a peculiar combined proliferation of mononuclear and multinucleated giant cells in a mesenchymal stromal background. Central and peripheral giant cell granulomas may have similar pathogenesis and histology but differ in their location and biological behaviour. It is important to differentiate them from other giant cell lesions that can occur in the oral cavity, such as giant cell tumour of the bone, aneurysmal bone cyst, brown tumour of hyperparathyroidism, and giant cell lesions of Ramon syndrome, Noonan syndrome, neurofibromatosis and Jaffe-Campanacci syndrome. A recent insight into their molecular genetics and pathogenesis, with identification of KRAS, FGFR1 and TRPV4 mutations, allows for better diagnostic differentiation and opens the door to the use of pathway inhibitors in the treatment of recurrent or dysmorphic lesions. In this review, we provide an updated summary of the clinical and pathological features of oral cavity giant cell granulomas that help with their precise diagnosis and management.

De novo TRPV4 Leu619Pro variant causes a new channelopathy characterised by giant cell lesions of the jaws and skull, skeletal abnormalities and polyneuropathy

BACKGROUND

Pathogenic germline variants in Transient Receptor Potential Vanilloid 4 Cation Channel (TRPV4) lead to channelopathies, which are phenotypically diverse and heterogeneous disorders grossly divided in neuromuscular disorders and skeletal dysplasia. We recently reported in sporadic giant cell lesions of the jaws (GCLJs) novel, somatic, heterozygous, gain-of-function mutations in TRPV4, at Met713.

METHODS

Here we report two unrelated women with a de novo germline p.Leu619Pro TRPV4 variant and an overlapping systemic disorder affecting all organs individually described in TRPV4 channelopathies.

RESULTS

From an early age, both patients had several lesions of the nervous system including progressive polyneuropathy, and multiple aggressive giant cell-rich lesions of the jaws and craniofacial/skull bones, and other skeletal lesions. One patient had a relatively milder disease phenotype possibly due to postzygotic somatic mosaicism. Indeed, the TRPV4 p.Leu619Pro variant was present at a lower frequency (variant allele frequency (VAF)=21.6%) than expected for a heterozygous variant as seen in the other proband, and showed variable regional frequency in the GCLJ (VAF ranging from 42% to 10%). In silico structural analysis suggests that the gain-of-function p.Leu619Pro alters the ion channel activity leading to constitutive ion leakage.

CONCLUSION

Our findings define a novel polysystemic syndrome due to germline TRPV4 p.Leu619Pro and further extend the spectrum of TRPV4 channelopathies. They further highlight the convergence of TRPV4 mutations on different organ systems leading to complex phenotypes which are further mitigated by possible post-zygotic mosaicism. Treatment of this disorder is challenging, and surgical intervention of the GCLJ worsens the lesions, suggesting the future use of MEK inhibitors and TRPV4 antagonists as therapeutic modalities for unmet clinical needs.

Central giant cell granuloma of the maxilla: Long-term follow-up of a patient treated with an adjuvant corticosteroid

BACKGROUND

Central giant cell granuloma (CGCG) is one of the most intriguing lesions of the jaws and its nature has not yet been fully elucidated. Clinically, some CGCG behave more aggressively, while others have an indolent course. In cases of aggressive CGCG of the maxilla, effective personalized therapies are worth understanding.

CASE REPORT

We report here a challenging case of aggressive CGCG in a 15-year-old girl which was misdiagnosed as an endodontic lesion. Radiographically, a large osteolytic lesion involving the hard palate from the central incisor to the second premolar, extending into the nasal cavity, with loss of the lamina dura and cortical resorption was observed. The lesion expanded aggressively after extensive curettage. With possible mutilation and defects due to a more radical approach to the lesion, treatment with systemic prednisone and intralesional triamcinolone hexacetonide associated with a calcitonin nasal spray was instituted. The decision in favor of this therapeutic strategy was made after careful immunohistochemical analysis of calcitonin and glucocorticoid receptors. The H-score for the staining of glucocorticoid and calcitonin receptors in multinucleated giant cells was 222 and 153.6, respectively. The lesion reduced in size, and no adverse effects associated with medications were observed. Another curettage was performed, and only fibrous connective tissue was found. The patient is in follow-up for 11 years without evidence of recurrence.

CONCLUSION

Pharmacological agents hold clinical promise in cases of aggressive CGCG affecting the maxilla of pediatric patients. Investigating the expression of calcitonin and glucocorticoid receptors in order to plan treatment is very helpful in the decision to manage aggressive CGCG.

"Central giant cell granuloma" - An update

There are multiple lesions in the jawbones with a common histological character of the presence of osteoclast-like giant cells under one category - giant cell lesions. The central giant cell granuloma (CGCG) is the most common of all and is found to be more prevalent in the Indian population. The pathogenicity still remains an enigma and needs to be differentiated from other look-alike lesions in order to have proper treatment planning. Furthermore, CGCG specifically needs to be differentiated from central giant cell tumor to avoid mutilating surgeries. This article is an attempt to give an outline of the CGCG with updating of the latest information on the perception of this lesion.

KRAS mutations in brown tumor of the jaws in hyperparathyroidism

BACKGROUND

Brown tumors are giant cell-rich lesions that result from abnormal bone metabolism in hyperparathyroidism, one of the most common endocrine disorders worldwide. Brown tumors occasionally affect the jaws and, despite well-known clinical and microscopic features, their molecular pathogenesis remains unclear. We investigated the presence of pathogenic activating mutations in TRPV4, FGFR1, and KRAS in a cohort of brown tumors since these have recently been reported in giant-cell lesions of the jaws and non-ossifying fibromas of the bones (FGFR1 and KRAS), which are histologic mimics of brown tumors.

METHODS

We target sequenced 13 brown tumors of the jaws associated with primary or secondary hyperparathyroidism. As mutations in these genes are known to activate the MAPK/ERK signaling pathway, we also assessed the immunostaining of the phosphorylated form of ERK1/2 (pERK1/2) in these lesions.

RESULTS

KRAS pathogenic mutations were detected in seven cases (p.G12V n = 4, p.G12D n = 1, p.G13D n = 1, p.A146T n = 1). KRAS variants of unknown significance (VUS), p.A134T and p.E37K, were also detected. All samples showed wild-type sequences for FGFR1 and TRPV4 genes. The activation of the MAPK/ERK signaling pathway was demonstrated by pERK1/2 immunohistochemical positivity of the brown tumors´ mononuclear cells.

CONCLUSION

Mutations in KRAS and activation of the MAPK/ERK signaling pathway were detected in brown tumors of hyperparathyroidism of the jaws, expanding the spectrum of giant cell lesions whose molecular pathogenesis involve RAS signaling.