Multiple versus solitary giant cell lesions of the jaw: Similar or distinct entities?

Exploiting BRAF mutations in the therapeutic approach towards oral and maxillofacial tumors

Oral and maxillofacial tumors pose a significant clinical challenge due to their tendency to recur, despite advancements in surgical removal techniques. The jaw's intricate structure further complicates treatments and affects patient quality of life. Consequently, emphasis has shifted towards pharmacological interventions, to potentially reduce invasive surgical procedures. One promising approach targets BRAF mutations, specifically the common V600E mutation. BRAF, a critical protein kinase, regulates cell growth and differentiation via the RAS-RAF-MEK-ERK-MAP kinase pathway. A specific nucleotide change at position 1799, swapping Thymine (T) for Adenine (A), results in the V600E mutation, causing unchecked cell growth. This mutation is common in certain oral and maxillofacial tumors like ameloblastoma. A recent neoadjuvant therapy targeting BRAF, involving the use of dabrafenib and trametinib, has showcased a promising, safe, and effective strategy for organ preservation in the treatment of mandibular ameloblastoma. This convergence of molecular insights and targeted therapies holds the key to managing BRAF-mutated oral and maxillofacial tumors effectively, promising improved patient outcomes.

RASopathies for Radiologists

RASopathies are a heterogeneous group of genetic syndromes caused by germline mutations in a group of genes that encode components or regulators of the Ras/mitogen-activated protein kinase (MAPK) signaling pathway. RASopathies include neurofibromatosis type 1, Legius syndrome, Noonan syndrome, Costello syndrome, cardiofaciocutaneous syndrome, central conducting lymphatic anomaly, and capillary malformation-arteriovenous malformation syndrome. These disorders are grouped together as RASopathies based on our current understanding of the Ras/MAPK pathway. Abnormal activation of the Ras/MAPK pathway plays a major role in development of RASopathies. The individual disorders of RASopathies are rare, but collectively they are the most common genetic condition (one in 1000 newborns). Activation or dysregulation of the common Ras/MAPK pathway gives rise to overlapping clinical features of RASopathies, involving the cardiovascular, lymphatic, musculoskeletal, cutaneous, and central nervous systems. At the same time, there is much phenotypic variability in this group of disorders. Benign and malignant tumors are associated with certain disorders. Recently, many institutions have established multidisciplinary RASopathy clinics to address unique therapeutic challenges for patients with RASopathies. Medications developed for Ras/MAPK pathway-related cancer treatment may also control the clinical symptoms due to an abnormal Ras/MAPK pathway in RASopathies. Therefore, radiologists need to be aware of the concept of RASopathies to participate in multidisciplinary care. As with the clinical manifestations, imaging features of RASopathies are overlapping and at the same time diverse. As an introduction to the concept of RASopathies, the authors present major representative RASopathies, with emphasis on their imaging similarities and differences. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Thoughts on the Etiology of Cherubism

Cherubism is nowadays classified as an autoimmune disease and was first described in 1933. Although suspected at that time to be the result of defective tooth development, it was primarily classified as a bone disease caused by a mutation in the SH3BP2 gene. Despite a knock-in mouse model, phenotypic signs in the jaw area were not reproducible in this model. The features of classical cherubism can be attributed to a disturbed formation of the dental placode of the second molar. Since 2019, it has become clear that inhibition of the WNT pathway leads to the accumulation of SH3BP2 via tankyrase inhibition. As the dental placode is triggered via WNT (in epithelia) and MSX1 (in mesenchyme), aplasia of the second and third molars occurs due to a block in the WNT pathway. The mesenchymal part, which occurs prior to the body plan regulation of the WNT/MSX1 pathway, remains unaffected and provides the substrate for the giant cell granuloma. Considering macrophage polarization and the role of the extracellular matrix in general, cherubism is situated in the field of tension between autoimmune diseases and cancer. In this sense, we see the cause of cherubism in a WNT-related dysregulation, which can be proven postnatally in the neural crest-related tooth development of the replacement tooth ridge, both genotypically and phenotypically.

Efficacy and Toxicity of Calcitonin Treatment in Children with Cherubism: A Single-Center Cohort Study

Cherubism is a rare autosomal dominant disease characterized by expansile osteolytic jawbone lesions. The effect and safety of off-label calcitonin treatment during the progressive phase of the disease are not well described. In this retrospective study, we present data on the radiological response and adverse effects of subcutaneously administered calcitonin in a cohort of nine cherubism children (three female, six male). Two of the nine patients underwent two separate treatment courses with a significant off-treatment interval in between; therefore, a total of 11 treatment courses with a mean duration of 17.9 months (range <1 to 35, SD 10.8) were studied. To measure the response, the cumulative volume of cherubism lesions was calculated from available three-dimensional imaging. The primary outcome was the change in the volume of lesions during calcitonin treatment and only assessed for the eight treatment courses with a minimal duration of 6 months. A statistically significant reduction in the mean cumulative volume of lesions was seen regardless of treatment duration. Average volume reduction was highest in the first half year of treatment, with a gradual, ongoing reduction thereafter. For the secondary outcome, the change in the cumulative volume of lesions after treatment cessation was assessed for the seven treatment courses with follow-up imaging available. After six of these seven treatment courses, the cumulative volume increased again but remained undoubtedly smaller than the initial volume at the start of therapy. Adverse effects were assessed for all 11 treatment courses and occurred in 73% of them. Most adverse effects were mild and low grade, with the most severe being one grade 3 symptomatic hypocalcemia requiring hospitalization and early treatment termination. Calcitonin treatment seems effective and tolerable in treating actively progressing cherubism in children. However, further research is required to better understand the pharmacological treatment of cherubism, including also other drugs, dosing, and protocols. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Treatment of Progressive Cherubism during the Second Dental Transitional Phase with Calcitonin

Cherubism is an autosomal dominant disease with variable expression. Aggressive forms of untreated cherubism may lead to severe malformation of the maxillofacial skeleton, developing tooth germs and teeth. Scarcely described and empirically applied interventional therapies during active stages of the disease try to limit the damage and deformation caused by progression of expanding intraosseous lesions. The final goal is to minimize the need for corrective surgeries once progressive growth has halted and disease enters its quiescent phase. New insights into the pathophysiology of cherubism hypothesize a potential role for dental development and jaw growth in the (hyper)activation of the disease. Theoretically, this could guide the ideal moment of pharmacological interventions. In this case report, the off-label use of systemic calcitonin treatment is described, stressing particularly the potential importance of its appropriate timing and duration of treatment.

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).

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.

Imatinib has minimal effects on inflammatory and osteopenic phenotypes in a murine cherubism model

OBJECTIVE

Cherubism is a genetic disorder characterised by bilateral jawbone deformation. The associated jawbone lesions regress after puberty, whereas severe cases require surgical treatment. Although several drugs have been tested, fundamental treatment strategies for cherubism have not been established. The effectiveness of imatinib has recently been reported; however, its pharmaceutical mechanism remains unclear. In this study, we tested the effects of imatinib using a cherubism mouse model.

METHODS

We used Sh3bp2 P416R cherubism mutant mice, which exhibit systemic organ inflammation and osteopenia. The effects of imatinib were determined using primary bone marrow-derived macrophages. Imatinib was administered intraperitoneally to the mice, and serum tumour necrosis factor-α (TNFα), organ inflammation and bone properties were examined.

RESULTS

The cherubism mutant macrophages produced higher levels of TNFα in response to lipopolysaccharide compared to wild-type macrophages, and imatinib did not significantly suppress TNFα production. Although imatinib suppressed osteoclast formation in vitro, administering it in vivo did not suppress organ inflammation and osteopenia.

CONCLUSION

The in vivo administration of imatinib had a minimal therapeutic impact in cherubism mutant mice. To establish better pharmaceutical interventions, it is necessary to integrate new findings from murine models with clinical data from patients with a definitive diagnosis of cherubism.

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.