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Sinonasal bone lesions encompass a diverse spectrum, ranging from nonneoplastic and benign conditions to aggressive, malignant neoplasms. These lesions can affect individuals across various age groups, from pediatric to adult patients. Recognizing these entities is crucial, given the variability in treatment approaches, recurrence rates, and prognoses. This review explores the common and uncommon but distinctive bone lesions affecting the sinonasal region, highlighting key clinical, radiographic, morphologic, and genetic features for each. Additionally, we provide helpful tips on distinguishing and accurately classifying each lesion within its relevant differential diagnoses., Competing Interests: Disclosure The authors have nothing to disclose., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Introduction: Benign fibro-osseous lesions have long been an area of diagnostic difficulty due to overlapping of histological and radiological features. Differentiating between these lesions is crucial because of their unique pathogenesis and biological behavior. Ossifying fibroma (OF) and fibrous dysplasia (FD) are the most prevalent lesions. However, not all FD or OF exhibit the typical radiological and histopathological features. In such situations, molecular-level investigations could be essential for precise identification and differentiation., Aim: To evaluate the screening of GNAS and CDC73 mutations in blood and formalin fixed tumor tissues (FFTT) of FD and OF cases., Material and Methods: Six blood samples (three cases of FD and JOF each) and thirteen FFTT (six cases of FD and seven cases of JOF) were included in the study. DNA was extracted from peripheral blood samples using salting out method followed by whole exome sequencing. Multiple efforts were made to extract DNA from tumor tissues using various protocols, but no measurable yield was obtained., Results: DNA derived from blood samples gave successful DNA library preparation and subsequent exome sequencing data generation. We report a pathogenic GNAS mutation (exon8:c.G602A:p.R201H) associated with McCune-Albright syndrome and a novel benign mutation identified in a case of FD (GNAS(NM_000516.7):c.257+687_257+688del) whereas none of the subjects of JOF displayed GNAS and/or CDC73 mutation., Conclusion: Study observed mutations in GNAS gene in blood samples from FD cases. However, a limitation is that only DNA extracted from blood underwent successful exome sequencing. Potential reason for low-quality DNA extraction from tissue may be attributed to prior fixation procedures conducted on bone specimens., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier GmbH. All rights reserved.)

Objective: In this study, our aim was to develop and validate the effectiveness of diverse radiomic models for distinguishing between gnathic fibrous dysplasia (FD) and ossifying fibroma (OF) before surgery., Materials and Methods: We enrolled 220 patients with confirmed FD or OF. We extracted radiomic features from nonenhanced CT images. Following dimensionality reduction and feature selection, we constructed radiomic models using logistic regression, support vector machine, random forest, light gradient boosting machine, and eXtreme gradient boosting. We then identified the best radiomic model using receiver operating characteristic (ROC) curve analysis. After combining radiomics features with clinical features, we developed a comprehensive model. ROC curve and decision curve analysis (DCA) demonstrated the models' robustness and clinical value., Results: We extracted 1834 radiomic features from CT images, reduced them to eight valuable features, and achieved high predictive efficiency, with area under curves (AUC) exceeding 0.95 for all the models. Ultimately, our combined model, which integrates radiomic and clinical data, displayed superior discriminatory ability (AUC: training cohort 0.970; test cohort 0.967). DCA highlighted its optimal clinical efficacy., Conclusion: Our combined model effectively differentiates between FD and OF, offering a noninvasive and efficient approach to clinical decision-making., (© 2024 Wiley Periodicals LLC.)

Competing Interests: Declaration of competing interest The authors declare no conflict of interest.

Reactive lesions of the oral cavity are non-neoplastic proliferations occurring due to chronic irritation. Peripheral ossifying fibroma (POF) is a reactive lesion usually occurring on the interdental papilla. POF is predominantly found in the second decade of life with a definitive female predilection. This is a case report of a middle-aged male patient with gingival overgrowth in left lower back tooth region. Clinically, the lesion was asymptomatic, firm, pale pink and sessile but unusually large in size. Surgical excision of the lesion was done followed by histopathological confirmation with emphasis on the diagnosis. The case in question is interesting because of its large size and location., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: This systematic review aimed to incorporate published data regarding synchronous cemento-ossifying fibromas (COF), with an analysis of their demographic and clinicopathological characteristics., Material and Methods: Case reports and case series of synchronous COF were searched in PubMed, Web of Science, Scopus, EMBASE, and LILACS according to the PRISMA (2020) statement. Also, a manual search was carried out and the grey literature was assessed. A descriptive statistical analysis was performed., Results: Nineteen studies comprising 20 cases of synchronous COF were included. The mean age at diagnosis was 35 years (±13.8), with a predominance of female patients (n=12/60%). In 13 cases (65%) the mandible and the maxilla were affected simultaneously. In two cases (10%) first-degree relatives (parents or siblings) had been previously diagnosed with COF. The diagnostic hypotheses were reported in 8 cases (40%), with florid cemento-osseous dysplasia, ameloblastic fibroodontoma, calcifying cystic odontogenic tumor, osteoma and cementoblastoma being cited in the differential diagnosis. Among the cases with details about management (n=17), eleven were treated by surgical enucleation and/or excision (64.7%). Follow-up was provided for 10 cases (50%), with a mean period of 44.7±62.19 months. Recurrence occurred in three of informed cases., Conclusions: Synchronous manifestation of COF is rare. Female patients around the 3rd decade of life are more commonly affected. Bilateral involvement of the mandible and maxilla is the most common clinical presentation.

Juvenile ossifying fibroma (JOF) is an uncommon benign fibro-osseous lesion (BFOL) of the maxillofacial bones with a locally aggressive nature and a high recurrence rate. Murine Double Minute 2 (MDM2) is an oncogene located at chromosome 12 (12q13-15) that inhibits the tumor suppressor gene TP53. The presence of MDM2 gene locus amplification is a useful molecular adjunct in the evaluation of some sarcomas, including low-grade intramedullary osteosarcoma (LGIOS). JOF and LGIOS have some overlapping clinical and histopathological features. The aim of this study is to evaluate a series of JOF for the presence of MDM2 gene locus amplification using fluorescence in-situ hybridization (FISH)., Materials and Methods: With IRB approval, a search of the institutional files of the archives of the Oral Pathology and Surgical Pathology biopsy services at the University of Florida Health was performed. The cases were re-evaluated by an oral pathology resident, an oral and maxillofacial pathologist, and a bone and soft tissue pathologist. Cases with consensus in diagnosis were selected (n = 9) for MDM2 testing. Testing by FISH for MDM2 gene locus amplification was applied to all retrieved cases., Results: The examined cases were all negative for MDM2 gene locus amplification via FISH testing., Conclusion: In our small series, JOF did not demonstrate MDM2 gene locus abnormality, a characteristic of LGIOS. This finding suggests that JOF has a distinct underlying pathogenesis. If confirmed in a larger series, these findings may be useful in distinguishing these two entities in cases with overlapping features or when minimal biopsy material is available., (© 2024. The Author(s).)

Abstract: Hybrid tumors are rare lesions having features of multiple diseases in one lesion. A hybrid tumor of central giant cell granuloma (CGCG) and central ossifying fibroma (COF) shows the presence of microscopically large areas with CGCG character and large areas with COF features inside a single clinical lesion, separated by a transition zone. A rare type of COF is juvenile ossifying fibroma (JOF)-trabecular variant in the mandible. We present a unique and rare case of a hybrid tumor of the CGCG-JOF-trabecular variant in the mandible of a 14-year-old female which initially diagnosed with CGCG. The ambiguous pathogenesis of hybrid tumors and giant cells is reviewed. The goal of this article is to highlight the importance of careful clinical, radiological, and histopathological examination of each case to prevent misdiagnoses and recurrences. Similar and other cases must be reported in order to better understand the interrelationship between these hybrid lesions and their biological behavior., (Copyright © 2023 Copyright: © 2023 Indian Journal of Pathology and Microbiology.)

Background: Indistinct and analogous histopathological features of various fibro-osseous lesions make establishing a definitive diagnosis a challenge. There is a need for additional molecular and histochemical tools to support and differentiate these lesions in order to establish a concrete diagnosis., Materials and Methods: A retrospective analysis of biopsied lesions in formalin-fixed paraffin-embedded sections (10 cases each of fibrous dysplasia, ossifying fibroma, and cement-osseous dysplasia) retrieved from the archives was studied for immunoexpression of osteocalcin (quantitative analysis in osteocytes), collagen characterization using Azan, Picrosirus, and Toluidine blue stain for evaluating intensity and localization of collagen fibers, and morphometric analysis of vasculature (for evaluating mean vessel density as square microns)., Results: Positive immunostaining of osteocalcin suggested mutations of the GNAS-1 gene found in fibrous dysplasia indirectly, as it is a negative regulator of bone formation. Osteocalcin immunopositivity was quantitatively measured in the fibro-osseous lesions, with fibrous dysplasia measuring 14.47 ± 3.628 as compared to ossifying fibroma measuring 5.23 ± 1.33, followed by cemento-osseous dysplasia measuring 2.30 ± 1.409. Toluidine blue suggests the presence of oxytalan fibers (resistant to acid hydrolysis) in ossifying fibroma and cemento-osseous dysplasia, pointing toward the pathogenesis of the lesion. Azan stain and Picrosirus (under a polarizing microscope) helped in distinguishing hard tissue characteristics (70% of cases of fibrous dysplasia showed only a magenta component followed by intermixed magenta with a blue component in 20% of cases and only 10% of cases showed magenta with blue borders whereas for ossifying fibroma, 40% of cases depicted magenta with blue borders along with the other 40% with intermixed magenta with blue component). The mean vessel density was also highest in fibrous dysplasia measuring 7.90 ± 1.079 (in Sq. micron area), followed by ossifying fibroma and cemento-osseous dysplasia., Conclusion: The diagnosis of fibro-osseous lesions by hematoxylin and eosin alone is confusing and thus should be supported by relatively simple histomorphometric analysis for better treatment outcomes. At the diagnostic stage of fibro-osseous lesions, evaluation of intralesional vessel size, reliable molecular marker, and histochemical nature can aid in differentiating fibrous dysplasia from central ossifying fibroma and cemento-osseous dysplasia alongside, other clinical, radiographic and pathological criteria. These parameters help in the diagnostic decision-making of fibro-osseous lesions., (Copyright © 2024 Copyright: © 2024 Indian Journal of Pathology and Microbiology.)

Abstract: Ossifying fibromyxoid tumor (OFMT) is a rare mesenchymal tumor of uncertain histogenesis with intermediate malignant potential presenting commonly in the fifth to sixth decade in the proximal limb and limb girdle. A 65-year-old male patient presented with a slow-growing gluteal mass. Wide local excision performed showed a well-defined tumor in the subcutaneous plane with a partially hard outer shell. Microscopy showed a moderately cellular tumor having cords and nests of round to ovoid cells with moderate cytoplasm and bland nuclei embedded in a myxo-hyaline matrix. An incomplete peripheral rim of ossification was seen. Pleomorphism/high cellularity was not seen. Mitosis was <2/50 high-power field. On immunohistochemistry, both S100 and desmin were positive. A diagnosis of typical OFMT was rendered. Even though rare with many morphological mimics, OFMT should be diagnosed with precision as most of these tumors are low-grade tumors that require only wide local excision and close follow-up without any adjuvant therapy., (Copyright © 2023 Copyright: © 2023 Indian Journal of Pathology and Microbiology.)

Introduction: Peripheral ossifying fibroma (POF) is a solitary gingival growth thought to arise from the gingiva, periosteum or the periodontal ligament. It is a slow-growing, benign, progressive lesion that is limited in size., Case Description: This article describes a case of ossifying fibroma of a peripheral variant that occurred in a 26-year-old female in the anterior region of the lower jaw and presented as a growth on the gingiva. Since it was difficult to diagnose clinically, a pathological evaluation was mandatory. Upon pathological confirmation of the diagnosis, the lesion was surgically excised up to the periosteum. This was deemed to be the required treatment yet, since the recurrence rate is high for POF (8% to 20%), the patient must be followed up yearly to check for recurrence., Competing Interests: All authors declare that there are no competing interests (financial or professional) that may be perceived to influence the research conducted., (Copyright © 2024 CDHA | ACHD.)

Rhabdomyosarcoma (RMS) with TFCP2 rearrangement has been identified recently. This entity has a distinctive clinicopathologic features: a rapidly aggressive clinical course, a preference for the craniofacial bones, a spindle and epithelioid histomorphology, and positive immunohistochemistry for epithelial markers, ALK, and myogenic markers. RMS with TFCP2 rearrangement is rare and may be misdiagnosed as other spindle cell tumors. Here, we report a case of this entity arising in the mandible, which was initially diagnosed as ossifying fibroma in primary tumor in another hospital. A 26-year-old man presented with a recurred mass in the mandible for 1 month after the operation of mandibular tumor. The first excisional specimen was initially diagnosed as ossifying fibroma in another hospital. Histopathologic examination revealed the tumor with a hybrid spindle cell and epithelioid cytomorphology, spindle cells and spindle-to-epithelioid cells with eosinophilic and rich cytoplasm, with high-grade features, prominent nucleoli and some atypical mitosis. Immunohistochemical analysis revealed positivity for desmin, MYOD1, pan-keratin, ALK (5A4), ALK (D5F3). Based on the morphology and immunophenotype, molecular studies were performed, which revealed a FUS::TFCP2 fusion transcript, confirming the diagnosis of Rhabdomyosarcoma with FUS::TFCP2 fusion. Making a correct diagnosis is primarily dependent on awareness by the pathologist of this rare subtype of RMS and careful histopathological evaluation, supported by immunohistochemical and molecular analysis, to avoid potential diagnostic pitfalls., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Purpose: The purpose of this study is to evaluate the association between hyperparathyroidism (PHPT), parathyroid hormone levels, and calcium levels in patients diagnosed with benign fibro-osseous lesions such as fibrous dysplasia (FD), ossifying fibroma (OF), central giant cell granulomas (GCG)., Methods: This is a retrospective, single-center study from a sample of patients who underwent surgical treatment of FD, OF, and GCG at Mayo Clinic between 1996 and 2021. Patient demographics, history of PHPT, histopathological diagnosis, and relevant laboratory values such as parathyroid hormone (PTH), serum calcium, vitamin D, and alkaline phosphatase were collected., Results: Of the patients diagnosed with FD (n = 64), OF (n = 24), and GCG (n = 5), a diagnosis of PHPT was found in 2 patients (3.1%), 1 patient (4.2%), and 0 patients (0%), respectively. Elevated PTH levels (>65 pg/mL) were observed in 3 patients (4.7%) with FD, 1 patient (4.2%) with OF, and 1 patient (20%) with GCG. Mean (standard deviation) calcium levels were 9.3 (0.6) mg/dL in the FD group, 9.4 (0.5) mg/dL in the OF group, and 9.3 (0.6) mg/dL in the GCG group. Patients with fibro-osseous jaw tumors including FD, OF, and GCG may have increased risk of PHPT compared to the general population., Conclusion: Patients with benign jaw tumors including FD, OF, and GCG may have increased risk of PHPT compared to the general population. Surgeons treating these benign tumors need to be cognizant of these findings, obtain appropriate laboratory studies, and incorporate multidisciplinary care including endocrinologists, endocrine surgeons, and maxillofacial surgeons., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Objectives: Gingiva is one of the supporting tissues around the teeth that can be affected by various neoplastic or nonneoplastic lesions. Previous studies have examined several types of gingival lesions, but the lack of a standardized classification system has hindered meaningful comparisons. Additionally, many studies focused primarily on reactive lesions. Our study aims to contribute to the understanding of gingival lesions by investigating their prevalence across age groups, genders, sites, and by their clinical presentation. This research could lead to improved diagnostic accuracy and treatment strategies., Materials and Methods: This retrospective study explores the prevalence of gingival lesions based on biopsies during a 22-year span. The patient's demographic details, including age, gender, and lesion's clinical presentation were systematically collected. These lesions were categorized into six groups. Descriptive statistics, χ 2 test of independence, and one-way ANOVA were used for data analysis., Results: Among the 7668 biopsied lesions, 684 (8.9%) lesions were located in the gingiva, with a greater occurrence in women (63.5%). Soft tissue tumors represented the most prevalent group in the gingival lesions (72.1%), and peripheral giant cell granuloma (PGCG) was the most frequent lesion (21.2%), followed by, pyogenic granuloma (19.3%), peripheral ossifying fibroma (17.8%) and focal fibrous hyperplasia (7.6%); all of which predominantly affected women, with mean ages falling in the fourth decade of life. Squamous cell carcinoma was recognized as the most common malignancy., Conclusion: In this study, PGCG was found to be the most common lesion in the gingiva in Iranian population. Further analysis using a unanimous categorization is required to confirm these results., (© 2024 The Authors. Clinical and Experimental Dental Research published by John Wiley & Sons Ltd.)

Background: Peripheral ossifying fibroma is a nonneoplastic inflammatory hyperplasia that originates in the periodontal ligament or periosteum in response to chronic mechanical irritation. Peripheral ossifying fibroma develops more commonly in young females as a solitary, slow-growing, exophytic nodular mass of the gingiva, no more than 2 cm in diameter. While various synonyms have been used to refer to peripheral ossifying fibroma, very similar names have also been applied to neoplastic diseases that are pathologically distinct from peripheral ossifying fibroma, causing considerable nomenclatural confusion. Herein, we report our experience with an unusual giant peripheral ossifying fibroma with a differential diagnostic challenge in distinguishing it from a malignancy., Case Presentation: A 68-year-old Japanese male was referred to our department with a suspected gingival malignancy presenting with an elastic hard, pedunculated, exophytic mass 60 mm in diameter in the right maxillary gingiva. In addition to computed tomography showing extensive bone destruction in the right maxillary alveolus, positron emission tomography with computed tomography revealed fluorodeoxyglucose hyperaccumulation in the gingival lesion. Although these clinical findings were highly suggestive of malignancy, repeated preoperative biopsies showed no evidence of malignancy. Since even intraoperative frozen histological examination revealed no malignancy, surgical resection was performed in the form of partial maxillectomy for benign disease, followed by thorough curettage of the surrounding granulation tissue and alveolar bone. Histologically, the excised mass consisted primarily of a fibrous component with sparse proliferation of atypical fibroblast-like cells, partly comprising ossification, leading to a final diagnosis of peripheral ossifying fibroma. No relapse was observed at the 10-month follow-up., Conclusions: The clinical presentation of giant peripheral ossifying fibromas can make the differential diagnosis from malignancy difficult. Proper diagnosis relies on recognition of the characteristic histopathology and identification of the underlying chronic mechanical stimuli, while successful treatment mandates complete excision of the lesion and optimization of oral hygiene. Complicated terminological issues associated with peripheral ossifying fibroma require appropriate interpretation and sufficient awareness of the disease names to avoid diagnostic confusion and provide optimal management., (© 2024. The Author(s).)

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., Competing Interests: Disclosure The authors have nothing to disclose., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Introduction: Fibroma ossificans are usually well-defined tumours, but are rarely encapsulated. The choice of radical or conservative treatment is a challenge for the maxillofacial surgeon. The aim of this case report was to describe the particularities of the management of a case of ossifying fibroma of the mandible., Case Report: The patient was a 17-year-old housewife with a history of caesarean section. She presented with a mandibular swelling that had been evolving for 6 years, with no other functional signs and no change in general condition. Exobuccal examination revealed a voluminous symphyseal swelling, covered by healthy-looking skin, with a bony consistency and forming part of the mandible. On endobuccal examination, there was a vestibular swelling extending from 36 to 45, covered by healthy-looking mucosa, with the absence of teeth 31, 32, 41, 42 and 43 and mobility of teeth 33 and 34. The hypothesis of a benign tumour of the mandible was raised. A maxillofacial CT scan revealed a heterogeneous image with local areas of hyperdensity and blowing of the external cortex. Treatment consisted of an interrupting mandibular resection via the vestibular approach, followed by transitional reconstruction using a stent graft. Histological examination of the surgical specimen revealed an ossifying fibroma. The outcome was favourable, with no recurrence after approximately 2 years., Conclusion: Treatment of ossifying fibroids can often be mutilating. It is discussed according to the clinical and radiological characteristics of the lesion., (Le comité de rédaction se réserve le droit de renvoyer aux auteurs avant toute soumission à l'avis des lecteurs les manuscrits qui ne seraient pas conformes à ces modalités de présentation. En outre il leur conseille de conserver un exemplaire du manuscrit, des figures et des tableaux.)

Cemento-ossifying fibroma (COF) is a mesenchymal benign odontogenic tumor, which may lead to impacted or ectopic permanent teeth. Autotransplantation of teeth is a surgical process, in which a tooth is transplanted from one position to another in the same individual. This method can effectively restore the patient's mastication and aesthetics and is feasible in replacing missing teeth. This study reports a case of simultaneous COF resection combined with heterotopic canine autotransplantation to repair dentition defect, which effectively promotes the restoration of bone continuity and stability and achieves immediate and long-term aesthetic function requirements.

Introduction: Ossifying fibromas are rare, non-aggressive benign tumours of the bone, commonly involving the posterior mandible in middle-aged individuals with a female predilection., Findings: Clinical manifestations include asymptomatic expansion of the mandible with infrequent maxillary lesions, pain, malocclusion, and compromised quality of life including aesthetic perception. Owing to multiplicity of features, tendency of recurrence, and possibility of malignant transformation, the diagnosis, treatment, and post-operative management of ossifying fibroma are always a challenge., Takeaway Lessons: Study aims to report a clinical case of extensive swelling involving the coronoid process and condyle on the right side to crossing the mid-line of the mandible with compromised functions and aesthetics. The article describes the clinical, histopathological, and radiological features of the case. The possible treatment and challenges encountered are discussed., (Copyright © 2024 Copyright: © 2024 Indian Journal of Dental Research.)

Cemento-ossifying fibroma (COF) and juvenile ossifying fibroma (JOF) have been considered distinct entities within the category of fibro-osseous lesions. This study aimed to assess osteoblast and osteoclast activity in COF and JOF by investigating bone resorption markers, specifically receptor activator of nuclear factor-kB (RANK), RANK ligand (RANKL), and its inhibitor osteoprotegerin (OPG). A comparative analysis of these markers was performed on all lesions. Immunohistochemistry was employed to evaluate and quantify the expression of these biomarkers in a sample of 20 cases of cemento-ossifying fibroma (COF), 15 cases of psammomatoid juvenile ossifying fibroma (PsJOF), and 10 cases of trabecular juvenile ossifying fibroma (TrJOF). The expression of osteoprotegerin was significantly higher in cemento-ossifying fibroma (33.9±13.0) compared to trabecular juvenile ossifying fibroma (27.3±9.2) and psammatoid ossifying fibroma (25.2±14.9), with the COF showing the highest expression followed by the latter two (p=0.037). There was a higher percentage (80%) of stromal fibroblast cells that showed positive expression of RANKL in cemento-ossifying fibroma (COF) compared to psammomatoid juvenile ossifying fibroma (PsJOF) (33.3%) and trabecular juvenile ossifying fibroma (TrJOF) (30.0%) when considering a positive expression score of 3 (p=0.024). Cemento-ossifying fibroma demonstrated the highest expression of osteoprotegerin and RANKL-positive stromal fibroblast cells, followed by psammomatoid juvenile ossifying fibroma and trabecular juvenile ossifying fibroma. These findings provide valuable insights into the pathogenesis of these lesions., Competing Interests: The author declares no conflict of interest., (©2023 JOURNAL of MEDICINE and LIFE.)

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., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Background: Ossifying fibroma of the paranasal sinuses and skull base in paediatric patients is difficult to operate and can recur easily after surgery. This study aimed to analyse factors associated with recurrence after transnasal endoscopic resection of ossifying fibroma in paediatric patients., Methods: This retrospective observational study included 34 patients under 17 years of age who underwent transnasal endoscopic resection of ossifying fibroma of the paranasal sinuses and skull base from 2005 to 2021 at a single tertiary medical centre. Clinical indicators such as age; surgical history; pathological type; intraoperative bleeding; and orbit, anterior skull base, sphenoid bone, sella turcica, clivus, or frontal sinus involvement were subjected to univariate analysis using the χ 2 test, to investigate whether any of these factors affected recurrence., Results: All 34 patients underwent transnasal endoscopic resection. The follow-up period was 6-120 months (mean: 48.0 months). Five patients experienced local recurrence during the follow-up period (14.7%). Results of χ 2 tests indicated that a history of previous surgery, the amount of intraoperative bleeding, and sphenoid and/or sella turcica and clivus involvement were significantly associated with recurrence (P < 0.05). Age; pathological stage; and orbit, anterior skull base, and frontal sinus involvement were not associated with recurrence (P > 0.05)., Conclusions: The increased risk of recurrence after transnasal endoscopic resection of nasal-skull base ossifying fibroma should be considered during endoscopic surgery in paediatric patients with a history of previous surgery, intraoperative bleeding tendency, and sphenoid and/or sella turcica and clivus involvement. These patients require careful postoperative follow-up., (© 2023. The Author(s).)

Peripheral ossifying fibroma (POF) is a reactive, benign gingival enlargement. Its etiology is not fully known. It can be seen in many different sizes in the mouth. The histopathological appearance of POF is mineralized tissue and fibrous proliferation. All relevant soft and hard tissues must be removed to prevent recurrence. Periodontal tissue remaining after excision is important for tooth preservation. With large lesions, the loss of healthy periodontal tissue is also large. Periodontal surgical approaches are important to preserve the remaining periodontal tissue. The positive effects of autogenously obtained titanium-prepared platelet-rich fibrin (T-PRF) and connective tissue graft (CTG) on soft tissue are well known. A 34-year-old woman presented with a fibrous and pedunculated gingival mass in the upper left canine premolar region. The operation was performed with complete excision of the lesion down to the bone along with the surrounding healthy tissue. Periodontal treatment of the large defect created after excision of a large POF lesion was performed with laterally positioned flap, CTG and T-PRF. The periodontal tissue and defect were noted to heal in a healthy manner at the 6-month follow-up. POF is a benign lesion; however, it has a high recurrence rate. Complete elimination of the lesion is crucial to prevent recurrence. Periodontal surgical methods and biomaterials applied after surgical excision are significant to maintain the periodontal health of the remaining teeth and tissues.

Background: gingival/alveolar mucosal reactive hyperplastic lesions (GRHL), including fibrous hyperplasia (FH), pyogenic granuloma (PG), peripheral ossifying fibroma (POF) and peripheral giant cell lesion (PGCL), are a common group of oral diseases. The aim of the present study was to access the frequency and distribution of the clinical and histological features of these disorders in a Brazilian population., Material and Methods: all specimens diagnosed as GRHL in three Oral Pathology laboratories were selected for the study. Clinical information was retrieved from the laboratory biopsy forms and hematoxylin and eosin stained histological slides were reviewed for analysis of the histological characteristics., Results: final sample was composed of 996 specimens, including 463 FH (47%), 280 PG (28%), 183 POF (18%) and 70 PGCL (7%). Females were more affected by FH, PG, and POF, and most cases affected adults with mean ages ranging from 40 to 53 years. FH, PG, and POF were more common in the upper gingiva/alveolar mucosa. Most PG, POF and PGCL were pedunculated, in contrast with FH (p<0.001). PG, FH and POF were mostly red or normal mucosal in color, while PGCL were mostly red/purple (p<0.001). PGCL were larger, followed by POF, FH and PG (p<0.001). Some histological features were characteristically found in some conditions, but they were also encountered in other lesions with variable frequencies., Conclusions: Oral medicine specialists, oral pathologists and periodontists are usually the professionals in contact with patients presenting GRHL and it is of upmost relevance that they should be familiarized with their clinical and histological profile.

Ossifying fibromyxoid tumors (OFMTs) are rare mesenchymal neoplasms which typically present in the superficial subcutaneous tissues and have not been reported to arise in visceral organs. We now report 4 molecularly confirmed cases of OFMT involving the genitourinary tract. All patients were males, ranging in age from 20 to 66 years (mean: 43 y). One case each arose in the kidney, ureter, perirenal soft tissue, and penis. All neoplasms demonstrated bland epithelioid to spindled cells set in a variably fibrous to fibromyxoid stroma, and only 1 had a peripheral shell of lamellar bone. All cases appeared well-circumscribed on gross/radiologic examination, though the primary renal neoplasm permeated between native renal tubules. By immunohistochemistry, S100 protein was negative in all 4 cases, while desmin was positive in 2 cases. In 2 cases, the Illumina TruSight RNA Fusion Panel demonstrated a PHF1::TFE3 and EP400::PHF1 fusion, respectively. In the remaining 2 cases, PHF1 gene rearrangement was confirmed by fluorescence in situ hybridization analysis. Due to unusual clinical presentation, lack of S100 positivity, and only occasional bone formation, the correct diagnosis was challenging in the absence of molecular testing. In summary, OFMT may rarely present primarily in the genitourinary tract. Given their nonspecific morphology and immunophenotype, molecular analysis is crucial to establish the correct diagnosis., Competing Interests: Conflicts of Interest and Source of Funding: Supported in part by: P50 CA217694 (C.R.A.), P30 CA008748 (C.R.A.), Kristin Ann Carr Foundation (C.R.A.), Dahan Translocation Carcinoma Fund and Joey’s Wings (P.A.). The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Purpose: Gingival fibromas (GFs) are fibrous lesions of the gingiva that are not well defined in the literature. They are histologically similar to peripheral ossifying fibromas (POFs), both being characterized as cellular proliferations of dense fibrous tissue, with POFs differing in that they demonstrate foci of calcification. This study aims to expand upon the immunohistochemical characterization of GFs, and to confirm their osteoblastic phenotype., Methods: Formalin fixed, paraffin embedded GFs, POFs and fibroepithelial polyps (FEPs) of the gingiva were examined. Immunohistochemical staining was performed for special AT-rich sequence binding protein 2 (SATB2), runt-related transcription factor 2 (RUNX2), osteocalcin and alpha-smooth muscle actin (αSMA). Sections were evaluated by light microscopy and the immunohistochemical staining patterns were assigned immunoreactive scores (IRS) based on percentage of stained cells and intensity of staining., Results: GFs, POFs, and FEPs of the gingiva expressed osteoblastic markers SATB2, RUNX2 and osteocalcin. GFs and POFs expressed αSMA while FEPs of the gingiva did not. GFs and POFs had similar staining patterns of SATB2, RUNX2 and αSMA., Discussion: These findings demonstrate that GFs and POFs exhibit a similar immunohistochemical profile, and supports a theory that GFs are osteoblastic lesions possibly related to POFs., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Aims: Ossifying fibromyxoid tumor (OFMT) is a rare enigmatic tumor of uncertain differentiation that can be classified as typical, atypical, and malignant subtypes based on cellularity, nuclear grade, and mitotic activity. The majority of OFMTs, regardless of the risk of malignancy, harbor genetic translocations. We report two malignant OFMTs, including one with evidence of dedifferentiation, with novel genefusions., Methods and Results: Case 1 was a 63-year-old male with a dedifferentiated OFMT arising in the right wrist, while case 2 was a 41-year-old male with a malignant OFMT presenting as a posterior mediastinal mass. Case 2 showed multifocal expression with EMA and synaptophysin, while desmin and S100 were absent in both tumors. NGS sequencing studies detected PHF1::FOXR1 and PHF1::FOXR2 gene fusions in cases 1 and 2, respectively. Despite aggressive regimens, both progressed with wide spread metastases resulting in death within six years of diagnosis., Conclusions: We expand the genetic spectrum of OFMTs with two novel gene fusions, PHF1::FOXR1 and PHF1::FOXR2. These cases confirm the previously reported tendencies for OFMTs with rare variant fusions to demonstrate malignant behavior, unusual morphology, and non-specific immunophenotype., (© 2023 John Wiley & Sons Ltd.)

Background: To analyze the clinicopathological features of different histological subtypes of epulis, and evaluate the risk factors associated with recurrence., Materials and Methods: A retrospective study including 2971 patients was performed. The patients' sex, age, location, size, histological subtypes, recurrence information, oral hygiene habits, periodontitis symptoms and smoking history were retrieved from the patient medical records and follow-up information., Results: Among the 2971 cases, focal fibrous hyperplasia (FFH) was the most common lesion (60.92%), followed by peripheral ossifying fibroma (POF) (29.32%), pyogenic granuloma (PG) (8.08%) and peripheral giant cell granuloma (PGCG) (1.68%). The peak incidence of epulis was in the third and fourth decade of life, with a mean age of 45.55 years. Female predominance was found in all types of lesions with a female to male ratio of 1.71:1. PG had the highest recurrence rate (17.18%), followed by POF (12.98%), FFH (9.55%) and PGCG (8.82%). Histological subtypes were significantly correlated with the recurrence of epulis (P = 0.013). Regular supportive periodontal therapy (P = 0.050) had a negative correlation with recurrence, whereas symptoms of periodontitis (P < 0.001) had a positive correlation with the recurrence of epulis., Conclusions: Controlling the periodontal inflammation and regular supportive periodontal therapy might help reduce the recurrence of epulis., (© 2023. The Author(s).)

Fibro-osseous lesions is a class of diseases with obvious similarities in clinical manifestations and pathological features, which has been attracting the attention of clinicians and pathologists. The latest WHO 2022 Classification (5th edition) included six of these diseases (cemento-osseous dysplasia, segmental odontomaxillary dysplasia, fibrous dysplasia, juvenile trabecular ossifying fibroma, psammomatoid ossifying fibroma and familial gigantiform cementoma) in the " fibro-osseous tumours and dysplasias ", and put forward new ideas on the diagnosis and treatment of these diseases. According to the latest WHO 2022 Classification (5th edition), the clinical and pathological features, diagnosis and differential diagnosis of these six diseases were described.

Cemento-ossifying fibroma (COF) is a benign mesenchymal odontogenic tumor that commonly occurs in the tooth-bearing areas of the maxilla and mandible. This study reports a COF case located under the left buccal mucosa. The classification and differential diagnosis of this COF case were discussed based on the diagnosis and treatment of this case and previous literature.

Background: Peripheral Ossifying Fibroma (POF) is a reactive hyperplastic lesion that exclusively occurs in the gingiva and is characterized by the deposition of dystrophic calcification, cementum-like tissue, and immature and mature bone within the connective tissue. The objective of the present study was to perform a retrospective analysis of clinicopathologic features of POF., Material and Methods: Clinical and histopathological data were obtained from biopsy records and histopathological reports from a Brazilian reference service in Oral Pathology (1999 - 2020). Morphological analysis was performed to evaluate features related to the mesenchymal component, inflammatory infiltrate, ulceration, and mineralized tissue., Results: A total of 270 POFs were diagnosed during the study period. A higher frequency was observed in females (71.9%) between the third (22.9%) and fourth (23.3%) decades of life. The anterior upper gingiva (29.1%) was the most affected region. Mature (86.7%) and immature (52.6%) bone tissue were the most frequent. There was a significant association between immature bone deposition and lesions with size ≤ 1.7 cm (p = 0.041); immature bone and cement-like tissue deposition with an evolution time ≤ 16 months (p < 0.001); deposition of immature bone and mesenchymal hypercellularization (p < 0.001); deposition of dystrophic calcification and the presence of ulceration (p < 0.001)., Conclusions: The clinical characteristics corroborate the findings in the literature. The heterogeneous distribution and quantity of mineralized tissues found in the analyzed cases support the theory that the different mineralized tissues constitute a spectrum of clinical maturation of POF.

Objective: To examine and compare the immunohistochemical expressions of IL-1β, IL-6, IL-17 and TNF-α in peripheral giant cell granuloma (PGCG) and peripheral ossifying fibroma (POF)., Design: The study included 20 POF and 20 PGCG cases diagnosed at the Pathology Department of Eskişehir Osmangazi University Medical Faculty. Hematoxylin & Eosin-stained slides obtained from each biopsy specimen were re-evaluated, and IL-1β, IL-6, IL-17 and TNF-α antibodies were investigated immunohistochemically. While staining in stromal cells was examined in POF cases, staining in both stromal spindle cells and multinucleated giant cells was evaluated in PGCG cases. An immunoreactivity score was established for each case by evaluating the staining percentage and intensity for each individual case. The significance level was set at 5% (p < 0.05)., Results: The level of IL-6 and TNF-α expressions in the multinucleated giant cells in PGCG lesions was found higher than that in stromal cells (p < 0.005 and p < 0.000, respectively). In PGCG lesions, there was no significant difference between giant cells and stromal cells in terms of IL-1β and IL-17 expression levels. There was no significant difference between PGCG and POF lesions in terms of IL-1β and IL-6 expression. TNF-α expression levels were significantly higher in spindle cells of PGCG lesions than that of POF lesions (p < 0.00). However, IL-17 expression levels were significantly lower in PGCG lesions than in POF lesions (p < 0.05)., Conclusion: The study results showed that TNF-α expression was significantly higher in PGCG lesions and IL-17 expression in POF lesions. IL-1β, IL-6, IL-17 and TNF-α are involved in the pathogenesis of both PGCG and POF lesions., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

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., (© 2021. The Author(s).)

Ossifying fibromas of the head and neck region are classified as cemento-ossifying fibroma (COF) (odontogenic origin), and two types of juvenile ossifying fibromas: juvenile trabecular ossifying fibroma (JTOF), and juvenile psammomatous ossifying fibroma (JPOF). The potential for recurrence in JTOF and JPOF and the discovery of newer molecular signatures necessitates accurate histological classification. Over 12 years (2005-2017), a total of 45 patients with 51 tumours were retrieved and reviewed for clinic-pathological features from the archives of a tertiary care oncology centre. Of 45 cases, COF, JTOF and JPOF comprised 13 (28.9%), 11 (24.4%) and 18 (40%) cases respectively. Three cases were unclassifiable. M: F ratio was 1:3.3, 1.1:1, 2:1 for COF, JTOF and JPOF respectively with an age range of 6-66 years (mean: 24.6, median; 18.1 years). The most common site for COF was mandible, for JTOF was maxilla, and for JPOF was ethmoid sinus. One case of mixed JTOF and JPOF histology was seen. Aneurysmal bone cyst-like areas were seen in 26.6% of cases, most commonly in JPOF. Follow up was available in 23 cases, and ranged from 4 to 207 months. Three cases of JPOF had a recurrence and one patient with JTOF had residual disease after surgery. One case of COF demonstrated increased parathyroid hormone levels. COF, JTOF, and JPOF are clinically, radiologically and histologically distinct entities. Surgical resection is the mainstay of treatment. JPOF has a higher incidence of recurrence as compared to JTOF and COF and hence needs a more aggressive follow-up., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Ossifying fibromyxoid tumor (OFMT) is a rare mesenchymal neoplasm of uncertain line of differentiation that can be subdivided into typical, atypical, and malignant tumors. Cytogenetically, OFMT is characterized by recurrent gene rearrangement involving PHF1 in up to 85% of cases. The most common PHF1 fusion partner is EP400, present in approximately half of cases. Most recently, a novel fusion of PHF1-TFE3 was identified in about 10% of PHF1-rearranged OFMTs. Herein, we report a unique case of PHF1-TFE3 fusion atypical OFMT with prominent collagenous rosettes. A 50-year-old male patient presented with a slowly growing, painless mass in the right foot for 4 years. Gross examination showed a 3.5-cm, subcutaneous well-circumscribed, lobulated mass. Microscopic examination revealed a well-demarcated but un-encapsulated tumor without a peripheral bony shell. The neoplasm was composed of mildly atypical spindle to ovoid cells with increased mitosis (2 mitoses per 10 high-power fields) arranged in a multinodular manner within a fibromyxoid stroma, which contained numerous small, irregular collagenous rosettes surrounded by radiating growth of tumor cells. The neoplastic cells were diffusely positive for TFE3 and CD10. RNA sequencing revealed an in-frame fusion between PHF1 exon 12 and TFE3 exon 7. Subsequent Fluorescence in-situ hybridization analyses demonstrated positive for rearrangements of both the PHF1 and TFE3 loci. The patient was free of disease at 63 months' follow-up. Our case exhibits atypical features and prominent collagenous rosettes, expanding the morphological spectrum of OFMT with PHF1-TFE3 fusion., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Myoepithelial tumors arising in soft tissue are uncommon and mostly manifest a benign clinical course, although a malignant form does exist. An EWSR1 gene rearrangement is a common event in these tumors. Ossifying fibromyxoid tumor, a rare soft tissue neoplasm of uncertain differentiation, may have overlapping histologic and immunophenotypic features with myoepithelial tumors, but frequently harbors a PHF1 gene rearrangement. Interestingly, a PHF1-TFE3 fusion has been recently reported in both entities. Here we report a case of a malignant soft tissue tumor demonstrating myoepithelial differentiation and harboring a PHF1-TFE3 fusion. Despite being slow-growing and lacking significant cytologic atypia at initial presentation, the patient deteriorated rapidly with local recurrence and distant metastases. A discussion of the potential clinicopathologic implications of a PHF1-TFE3 fusion in these entities is also developed., (Copyright © 2021 Elsevier GmbH. All rights reserved.)

Rationale: Several diseases feature tumors, or tumor-mimicking lesions, that further invade the bone and surrounding joints of the wrist region. Here, we describe 3 rare cases of multiple destructed carpal bones and adjacent joints in different disease entities confirmed via pathologic diagnosis., Patient Concerns: All 3 cases were examined between January 2016 and December 2019. Three patients presented with similar clinical manifestations and radiographic features, with multiple osteolytic lesions in the carpal bones and metacarpal bone base., Diagnoses: The 3 cases were diagnosed as diffuse type tenosynovial giant cell tumor, calcifying aponeurotic fibroma, and rheumatoid arthritis., Interventions: Separate, experienced radiologist and pathologist took part in the interpretation and compartmentalization of radiographs and pathological findings, respectively. Even magnetic resonance imaging could not achieve a diagnosis; surgical excision was therefore required, with subsequent pathological assessment for treatment and final diagnosis., Outcomes: functional outcomes also differed among patients, poorest in rheumatoid arthritis patient., Lessons: We report 3 rare disease entities, presenting with multifocal osteolytic lesions in the wrist. They all presented with similar clinical manifestations, and the final diagnoses were made via pathological evaluation. Compared with tenosynovial giant cell tumor and calcifying aponeurotic fibroma, rheumatoid arthritis had the poorest outcome., Competing Interests: The authors report no conflicts of interest., (Copyright © 2021 the Author(s). Published by Wolters Kluwer Health, Inc.)

Objective: To describe the presentation, diagnosis, treatment, and outcome for horses with fibro-osseous lesions of the craniofacial complex., Study Design: Retrospective multicenter case series., Animals: Thirty horses evaluated for fibro-osseous lesions of the skull from January 1, 2001 through December 31, 2019 in four centers., Methods: Medical records were reviewed for signalment, clinical presentation, histological and diagnostic imaging findings, treatment instituted, and outcome. Long-term outcome information was obtained by owner questionnaire or the medical record., Results: Diagnoses included ossifying fibroma in 20 of 30 horses, osteoma in eight of 30 horses, and fibrous dysplasia in two of 30 horses. Twelve of 30 lesions were diagnosed in horses <1 year old, and 20 of 30 lesions originated from the rostral mandible. The most common treatment was rostral mandibulectomy. Recurrence was not reported after complete excision. Incomplete excision was confirmed in eight horses (four ossifying fibromas, three osteomas, and one fibrous dysplasia), and follow-up information was available for seven horses. Recurrence occurred in one horse, while six horses had long-term resolution of clinical signs. Prognosis for survival and return to use was excellent in 23 horses with long-term follow-up., Conclusion: Fibro-osseous lesions were uncommon in this multicenter study; they were most commonly diagnosed in young animals and most frequently affected the rostral mandible. Long-term survival was excellent., Clinical Significance: The definitive diagnosis of fibro-osseous lesions of the craniofacial complex in horses is made from results of histopathology and cannot be determined on the basis of clinical presentation alone. Surgical excision is indicated, and prognosis can be favorable even when complete surgical margins are not obtained., (© 2021 The American College of Veterinary Surgeons.)

Objective: To undertake a differential diagnosis of a large mass found in the left maxillary sinus of a cranium dated to the 16th-17th-century, and to expand knowledge of the diagnosis of osseous tissue formation in osteoarchaeological studies., Material: A cranium recovered from the cemetery of San Salvador de Palat de Rey church, León (Spain)., Methods: Macroscopic analysis, CT scanning., Results: Macroscopic analysis indicated that the individual was probably a male over 30 years old with an ossified mass in the left maxillary sinus, measuring 24 × 19 × 24 mm, occupying approximately 27 % of the maxillary antrum. Computed tomography revealed a well-demarcated radiolucent unilocular mass with some radiopaque areas, with no communication with the alveoli of the premolars or molars. No erosive lesions or signs of inflammation were found., Conclusions: Neither the macroscopic, nor the radiological characteristics are compatible with inflammatory or malignant pathology, favoring a diagnosis of ossifying fibroma., Significance: This case adds to the few reported cases in the osteoarchaeological literature, especially since there is limited relevant reference data to assist diagnosis. The CT scans and 3D reconstruction presented here facilitate differential diagnosis in future paleopathological studies., Limitations: Destructive methods were not authorized., Suggestions for Further Research: In the future, micro-CT analysis, which was not performed in the current study, may add new and valuable information., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Objective: To report the exceptional occurrence of ossifying fibromyxoid tumour (OFMT) as a primary bone lesion. OFMT is a rare soft tissue tumour of uncertain differentiation and variable malignant potential, that occurs in adults with a slight male predominance. It is typically located in the subcutis or in the skeletal muscles of the extremities, followed by trunk or head and neck., Methods: Two cases of OFMT proven to arise from bone are presented. The first is a 65-year old female with a history of rib "osteosarcoma", presenting with an inferior lobe left lung mass. The second is a man with a lytic lesion of the 5th cervical vertebra that recurred shortly after resection. Following H&E and immunohistochemical examination, tumour samples were analysed by NGS and by break-apart FISH to detect rearrangement of the PHF1 and TFE3 genes., Results: PHF1 gene-rearrangement was identified by FISH on both the primary and the metastatic lesion of first patient. NGS identified a PHF1 (intron1) and EPC1 (exon 10) fusion transcript later confirmed by positive PHF1 rearrangement on FISH in the second case., Conclusions: The demonstration of PHF1 gene rearrangements represents a fundamental ancillary diagnostic test when presented with challenging examples of OFMT., (Copyright © 2020 Società Italiana di Anatomia Patologica e Citopatologia Diagnostica, Divisione Italiana della International Academy of Pathology.)