MDM2 and CDK4 immunohistochemistry is a valuable tool in the differential diagnosis of low-grade osteosarcomas and other primary fibro-osseous lesions of the bone

GLI1 amplification and fusion in MDM2-amplified low-grade osteosarcoma

AIMS

Glioma-associated oncogene homologue 1 (GLI1) was recently shown to be coamplified with mouse double minute 2 (MDM2), cyclin-dependent kinase 4 (CDK4) and some other adjacent genes in a significant subset of GLI1-altered mesenchymal tumours and well-differentiated/dedifferentiated liposarcomas, which are characterised by MDM2 amplification. Given that MDM2 is also amplified in low-grade osteosarcoma (LGOS), we investigated the prevalence of GLI1 amplifications/fusions in a series of 15 cases of MDM2-amplified LGOS, an area that has not been previously explored.

METHODS

This study conducted a retrospective analysis and examined GLI1 amplifications/fusions in 15 cases of MDM2-amplified LGOS and 46 cases of other bone tumours and tumour-like lesions using fluorescence in situ hybridisation with a GLI1 amplification probe and a GLI1 break-apart probe. Six cases of LGOS were also tested by next-generation sequencing.

RESULTS

Fluorescence in situ hybridisation analysis revealed that 13 of 15 (87%) LGOS cases exhibited GLI1 amplification; no fusion gene was found. Next-generation sequencing revealed that all six tested cases showed GLI1 amplification and one case had both GLI1 amplification and GLI1 gene fusion (PPM1H::GLI1). All 46 cases of other bone tumours and tumour-like lesions were negative for GLI1 amplification and GLI1 fusion.

CONCLUSION

These results indicate that GLI1 amplification is common in LGOS, and GLI1 fusion could occur in LGOS.

Mesenchymal Neoplasms of the Bladder and Male Genital Tract, including the Perineum and Scrotum

Mesenchymal neoplasms of the bladder and male genital tract are uncommonly encountered in routine diagnostic practice and present diagnostic challenges. Here, I systematically survey mesenchymal tumors at each body site, including the spermatic cord, scrotum, and perineum. I provide a detailed overview of tumor types that specifically or most commonly occur in the bladder and male genital tract, including pseudosarcomatous myofibroblastic neoplasm of the bladder, proliferative funiculitis, paratesticular sclerosing rhabdomyoma, penile myointimoma, and so-called prostatic stromal tumors.

Ongoing chromothripsis underpins osteosarcoma genome complexity and clonal evolution

Osteosarcoma is the most common primary cancer of the bone, with a peak incidence in children and young adults. Using multi-region whole-genome sequencing, we find that chromothripsis is an ongoing mutational process, occurring subclonally in 74% of osteosarcomas. Chromothripsis generates highly unstable derivative chromosomes, the ongoing evolution of which drives the acquisition of oncogenic mutations, clonal diversification, and intra-tumor heterogeneity across diverse sarcomas and carcinomas. In addition, we characterize a new mechanism, termed loss-translocation-amplification (LTA) chromothripsis, which mediates punctuated evolution in about half of pediatric and adult high-grade osteosarcomas. LTA chromothripsis occurs when a single double-strand break triggers concomitant TP53 inactivation and oncogene amplification through breakage-fusion-bridge cycles. It is particularly prevalent in osteosarcoma and is not detected in other cancers driven by TP53 mutation. Finally, we identify the level of genome-wide loss of heterozygosity as a strong prognostic indicator for high-grade osteosarcoma.

Ossifying fibroma and juvenile ossifying fibroma: A systematic review on clinical and radiological parameters, treatment modalities and recurrence

Ossifying fibroma (OF) is a rare benign fibro-osseous neoplasm developing mostly in maxillo-facial bones. OF is divided in cemento-ossifying fibroma (COF), juvenile trabecular ossifying fibroma (JTOF) and psammomatoid ossifying fibroma (PSOF). The aim of this systematic review was to synthetize the existing literature on OF, investigating the clinical and radiological parameters related to the different forms of the disease, and to compare the treatment modalities according to their associated recurrence rate. Three databases were searched in March 2024, with an update in September 2024. Eligibility criteria included studies reporting on patients with OF, surgical treatment and follow-up data. Of the 2016 studies identified, 22 were retained after eligibility assessment. A total of 492 patients were included. Most OF presented with painless swelling. COF affected 61.1 % of women with a mean age of 29.5, JTOF presented in 55.7 % of male children, and PSOF had no predilection for sex with a mean age of 19.5 years. Enucleation and curettage were associated with an elevated recurrence rate in JTOF (12/30) and PSOF (10/16). PSOF (6 cases) and JTOF (15 cases) showed no recurrence with radical surgery. Same recurrence rates in COF were seen for conservative and radical surgery. Although radical surgery seemed to avoid recurrence in JTOF and PSOF, conservative surgery such as enucleation and curettage with additional peripheral ostectomy should be considered primarily to lessen the morbidity induced by radical resection. Close clinical and radiological follow-up should be undertaken to diagnose early recurrence.

Primary Intraosseous Solitary Fibrous Tumor of the Mandible: Report of a Diagnostically Challenging Case with NAB2::STAT6 Fusion and Review of the Literature

INTRODUCTION

Solitary fibrous tumor (SFT) represents an uncommon mesenchymal neoplasm affecting primarily the extremities and deep soft tissues with, overall, benign but locally aggressive biologic behavior and an underlying pathognomonic NAB2::STAT6 fusion. Intraosseous SFTs are infrequent, and involvement of the jawbones is exceedingly rare.

CASE PRESENTATION

A 54-year-old woman presented with an asymptomatic, well-demarcated, multilocular radiolucency of the left posterior mandible featuring focally irregular borders, root resorption and lingual cortex perforation. The lesion had shown progressive growth over a 6-year period. Microscopically, a proliferation of predominantly ovoid and spindle-shaped cells with indistinct cell membrane borders, elongated, plump or tapered, hyperchromatic nuclei, and lightly eosinophilic cytoplasm was noted. Marked cytologic atypia, pleomorphism and mitoses were absent. A secondary population of epithelioid cells exhibiting ovoid or elongated vesicular nuclei, and abundant, pale eosinophilic or vacuolated cytoplasm was also present. The supporting stroma was densely fibrous with areas of marked hyalinization and variably-sized, ramifying, thin-walled vessels. By immunohistochemistry, lesional cells were strongly and diffusely positive for STAT6 and CD99, and focally immunoreactive for MDM2 and SATB2. Ki-67 was expressed in less than 5% of lesional cells, while most interspersed epithelioid cells were positive for the histiocyte marker, CD163. Molecular analysis disclosed a NAB2::STAT6 fusion confirming the diagnosis of SFT. The patient underwent segmental mandibulectomy.

CONCLUSIONS

Herein, we report the first case of primary intraosseous SFT of the mandible with complete documentation of its characteristic immunohistochemical and molecular features. Diagnosis of such unusual presentations may be further complicated by the challenging histomorphologic diversity of SFT.

Low-grade central osteosarcoma with extraosseous dedifferentiation: a rare case

Low-grade central osteosarcoma (LGCOS), which arises from the intramedullary cavity of the metaphysis of long bones, occasionally exhibits extraosseous spread. Approximately 10-30% of patients with LGCOS exhibit dedifferentiation, but it is rare to experience a primary tumor with a dedifferentiated component. A 38-year-old female patient presented with right knee pain for two months. Imaging studies revealed a bone mass with extraosseous involvement. Wide resection was performed, and pathologic examination led to the diagnosis of LGCOS with a dedifferentiated extraosseous lesion. A single defect in the bone cortex constituted the boundary between the low- and high-grade components. The extraosseous high-grade component included more tumor cells with p53 overexpression and more murine double minute 2 (MDM2) copies compared with the low-grade component. These genetic mutations and copy number alterations can be associated with malignant transformation of LGCOS.

Bizarre Parosteal Osteochondromatous Proliferation With Malignant Transformation and Metastases

A patient with a benign bizarre parosteal osteochondromatous proliferation (BPOP) located in the anterior knee was treated with resection in preparation for total knee arthroplasty (TKA). The BPOP reoccurred and was treated with re-resection at the time of TKA. The BPOP reoccurred a second time and underwent malignant transformation to a fungating high-grade pleomorphic sarcoma with metastatic lesions. This case highlights the rare potential of a previously benign BPOP to undergo malignant transformation after recurrence. A wide margin resection may be considered primarily when surgery is indicated to prevent recurrence and its potential sequelae. [Orthopedics. 2024;47(6):e322-e326.].

CDK4 is co-amplified with either TP53 promoter gene fusions or MDM2 through distinct mechanisms in osteosarcoma

Amplification of the MDM2 and CDK4 genes on chromosome 12 is commonly associated with low-grade osteosarcomas. In this study, we conducted high-resolution genomic and transcriptomic analyses on 33 samples from 25 osteosarcomas, encompassing both high- and low-grade cases with MDM2 and/or CDK4 amplification. We discerned four major subgroups, ranging from nearly intact genomes to heavily rearranged ones, each harbouring CDK4 and MDM2 amplification or CDK4 amplification with TP53 structural alterations. While amplicons involving MDM2 exhibited signs of an initial chromothripsis event, no evidence of chromothripsis was found in TP53-rearranged cases. Instead, the initial disruption of the TP53 locus led to co-amplification of the CDK4 locus. Additionally, we observed recurring promoter swapping events involving the regulatory regions of the FRS2, PLEKHA5, and TP53 genes. These events resulted in ectopic expression of partner genes, with the ELF1 gene being upregulated by the FRS2 and TP53 promoter regions in two distinct cases.

Assessment of MDM2 Gene Locus Amplification by Fluorescence In-Situ Hybridization in Juvenile Ossifying Fibroma

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.

MDM2 Amplification Status in a Cohort of Well-Characterized Myxofibrosarcoma: A Clinicopathologic Analysis of 22 Tumors

Myxofibrosarcomas (MFS) present as slowly enlarging superficial masses in elderly patients. Even though these tumors fail to exhibit a distinct immunophenotype, diagnosis is straightforward when they present in subcutaneous tissue. Intramuscular MFS, however, are more challenging to diagnose as the differential also includes dedifferentiated liposarcoma with myxoid features. The vast majority of dedifferentiated liposarcomas show MDM2 amplification, whereas limited data exists as to the MDM2 status of MFS. We sought to explore the rate of MDM2 amplification in cases of classic MFS. Our archives were searched for MFS; only subcutaneous well-sampled resections were included. FISH for MDM2 amplification was performed on each tumor. A cohort of myxoid dedifferentiated liposarcoma resections was studied for comparison. Twenty-two MFS arose in patients aged 44 to 85 years. All tumors contained an infiltrative population of atypical cells embedded in a myxoid stroma with curvilinear blood vessels. MDM2 amplification by FISH was identified in 3 (of 22; 14%) tumors. Available follow up on 17 patients (range 1-96 months; median 13 months) revealed 6 patients with local recurrence and 1 with distant metastasis. Of 3 patients with MDM2- amplified MFS, 1 experienced recurrence and died of unrelated causes, while the second was alive without disease 12 months after diagnosis. Even though the rate of MDM2 amplification by FISH in MFS appears to be low, a subset of cases may show this genetic alteration, which pathologists should be aware of to avoid misclassification as myxoid dedifferentiated liposarcomas. Further studies are necessary to determine if amplification status adds prognostic value.

Jaw Fibro-Osseous Lesions: Use of a Predictive Index in Grading Probable Malignant Changes and a Review of Cases

STATEMENT OF THE PROBLEM

Fibro-osseous lesions (FLs), may rarely exhibit malignant features likewise undergo malignant transformation. Awareness of these features can assist in screening for potentially malignant cases and identifying low-grade central osteogenic sarcoma (LGCOS) that may mimic FLs.

PURPOSE

The objective of this study was to determine the usability of an index in predicting malignant changes in jaw FLs.

MATERIALS AND METHOD

This was a retrospective study where hematoxylin and eosin (H&E) slides and archival records of fibrous dysplasia (FD) and ossifying fibroma (OF) cases were reviewed. The sections were assessed for permeation of marrow spaces, stromal growth pattern, cytologic atypia, mitotic activity, and pattern of bone growth, which are parameters for diagnosing LGCOS. The predictive histologic index of malignancy (PHIM) was determined by a sum of the scores and graded as 0=nil, 1=low, 2 & 3=moderate, and 4 & 5=high. Data were presented using descriptive analysis.

RESULTS

Ninety-three cases of FLs met the inclusion criteria, consisting of 40(43%) cases of FD and 53(57%) cases of OF. The peak age of presentation for FD and OF was 2nd and 3rd decade. There was a female preponderance of 1:1.6. The maxilla was the most common site affected by FD, while the mandible was most commonly affected by OF. For FD cases, the PHIM was moderate in 10(25%) cases and low in 21(52.5%) cases. Similarly, for OF cases, 30(56.6%) cases had low grade PHIM while 10(17%) cases had moderate grade PHIM.

CONCLUSION

The PHIM depicted low to moderate malignancy grade in some of the cases studied. Follow up studies would be necessary to assess the PHIM.

Retroperitoneal dedifferentiated liposarcoma with rare heterologous low-grade osteosarcoma: A case report

Dedifferentiated liposarcoma is a high-grade entity developed from a preexisting or recurrent well-differentiated liposarcoma, and rarely, it may contain divergent differentiation. We presented the case of a 39-year-old woman with retroperitoneal dedifferentiated liposarcoma with heterologous low-grade osteosarcoma, possessing a special pattern of tumoral calcification.

High-grade osteosarcoma arising in DCIA flap reconstruction after a prior resection of maxillar cemento-ossifying fibroma: A case report

Cemento-ossifying fibroma is a rare benign odontogenic tumour of the tooth-bearing jaws. Its concomitant occurrence with osteosarcoma, a malignant maxillofacial bone tumour, has never been described before. We present an uncommon case of a 43-year-old woman in whom a cemento-ossifying fibroma in the right maxilla was treated by resection and reconstruction using a deep circumflex iliac artery flap. During surgical prosthetic rehabilitation one-year post-operative, an osteosarcoma extending from the contralateral maxilla was coincidentally discovered in the deep circumflex iliac artery flap. The aim of this case report is to raise awareness on the extremely rare but possible simultaneous and independent occurrence of a cemento-ossifying fibroma and an osteosarcoma.

Unveiling the Protective Role of Melatonin in Osteosarcoma: Current Knowledge and Limitations

Melatonin, an endogenous neurohormone produced by the pineal gland, has received increased interest due to its potential anti-cancer properties. Apart from its well-known role in the sleep-wake cycle, extensive scientific evidence has shown its role in various physiological and pathological processes, such as inflammation. Additionally, melatonin has demonstrated promising potential as an anti-cancer agent as its function includes inhibition of tumorigenesis, induction of apoptosis, and regulation of anti-tumor immune response. Although a precise pathophysiological mechanism is yet to be established, several pathways related to the regulation of cell cycle progression, DNA repair mechanisms, and antioxidant activity have been implicated in the anti-neoplastic potential of melatonin. In the current manuscript, we focus on the potential anti-cancer properties of melatonin and its use in treating and managing pediatric osteosarcoma. This aggressive bone tumor primarily affects children and adolescents and is treated mainly by surgical and radio-oncological interventions, which has improved survival rates among affected individuals. Significant disadvantages to these interventions include disease recurrence, therapy-related toxicity, and severe/debilitating side effects that the patients have to endure, significantly affecting their quality of life. Melatonin has therapeutic effects when used for treating osteosarcoma, attributed to its ability to halt cancer cell proliferation and trigger apoptotic cell death, thereby enhancing chemotherapeutic efficacy. Furthermore, the antioxidative function of melatonin alleviates harmful side effects of chemotherapy-induced oxidative damage, aiding in decreasing therapeutic toxicities. The review concisely explains the many mechanisms by which melatonin targets osteosarcoma, as evidenced by significant results from several in vitro and animal models. Nevertheless, if further explored, human trials remain a challenge that could shed light and support its utility as an adjunctive therapeutic modality for treating osteosarcoma.

Diagnostic challenges in low-grade central osteosarcoma

Aims

Low-grade central osteosarcoma (LGCOS), a rare type of osteosarcoma, often has misleading radiological and pathological features that overlap with those of other bone tumours, thereby complicating diagnosis and treatment. We aimed to analyze the clinical, radiological, and pathological features of patients with LGCOS, with a focus on diagnosis, treatment, and outcomes.

Methods

We retrospectively analyzed the medical records of 49 patients with LGCOS (Broder's grade 1 to 2) treated between January 1985 and December 2017 in a single institute. We examined the presence of malignant features on imaging (periosteal reaction, cortical destruction, soft-tissue invasion), the diagnostic accuracy of biopsy, surgical treatment, and oncological outcome.

Results

Based on imaging, 35 of 49 patients (71.4%) exhibited malignant features. Overall, 40 of 49 patients (81.6%) had undergone a biopsy before en-bloc resection: 27 of 40 patients (67.5%) were diagnosed on the first biopsy, which was more accurate when carried out by open rather than needle biopsy (91.3% vs 35.3% diagnostic accuracy, respectively; p < 0.001). Of the 40 patients treated by en-bloc resection, surgical margins were wide in 38 (95.0%) and marginal in two (5.0%). Furthermore, nine of 49 patients (18.4%) underwent curettage (intralesional margin) without previous biopsy. All patients with a positive margin developed local recurrence. Distant metastases occurred in five of 49 patients (10.2%). The mean five-year overall survival (OS) and distant relapse-free survival (D-RFS) were 89.3% (SD 5.1%) and 85.7% (SD 5.5%), respectively. Univariate analysis showed that the occurrence of distant metastasis was a poor prognostic factor for OS (hazard ratio 11.54, 95% confidence interval (CI) 1.92 to 69.17; p < 0.001). Local recurrence was a poor prognostic factor for D-RFS (HR 8.72, 95% CI 1.69 to 45.0; p = 0.002).

Conclusion

The diagnosis of LGCOS can be challenging because it may present with non-malignant features and has a low diagnostic accuracy on biopsy. If precisely diagnosed, LGCOS can be successfully treated by surgical excision with wide margins.

Periosteal Fasciitis With Unusual Radiologic Features Harboring a Novel STAG1::USP6 Fusion Gene

Periosteal fasciitis is a subtype of nodular fasciitis originating from the periosteum. The diagnosis can be challenging and requires radiologic-pathologic correlation. Advances in molecular analysis confirmed that nodular fasciitis and its related lesions harbor a USP6 gene rearrangement with one of the several potential partners. Herein, we report a case of periosteal fasciitis with metaplastic bone formation detected incidentally during a radiologic survey for breast carcinoma. Radiologic examination revealed a 2.4 cm, heterogeneous, avidly enhancing lesion of the right femoral distal metaphysis concerning for low-grade periosteal chondrosarcoma. Histological examination of a core needle biopsy revealed a tumor composed of bland spindle cells with myofibroblastic and osteoblastic phenotypes admixed with immature bone and cartilaginous elements. Molecular analysis revealed a novel STAG1::USP6 fusion that helped arrive at the right diagnosis and further expands the molecular profile of USP6-associated neoplasms.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Unusual Site of a Bizarre Parosteal Osteochondromatous Proliferation (Nora's Lesion) Involving the Scapula: First Case Report and Review of the Literature

Bizarre parosteal osteochondromatous proliferation (BPOP), also known as Nora's lesion, is a rare benign surface lesion of bone that typically occurs in the hands and feet. We report herein the first case of BPOP occurring in an unusual location, specifically the scapula of a 29-year-old male patient. The lesion exhibited features mimicking those of a peripheral chondrosarcoma because of its atypical location in the axial skeleton and the presence of calcification, which indicates the presence of cartilaginous matrix. Treatment involved a wide surgical resection, and histopathological examination confirmed the diagnosis of BPOP of the bone. At a five-year follow-up, there was no evidence of local recurrence.

Craniofacial Fibrous Dysplasia: Clinical and Therapeutic Implications

PURPOSE OF REVIEW

This study aims to review diagnosis, potential complications, and clinical management in craniofacial fibrous dysplasia.

RECENT FINDINGS

Fibrous dysplasia (FD) is a rare mosaic disorder in which normal bone and marrow are replaced with expansile fibro-osseous lesions. Disease presents along a broad spectrum and may be associated with extraskeletal features as part of McCune-Albright syndrome (MAS). The craniofacial skeleton is one of the most commonly impacted areas in FD, and its functional and anatomical complexities create unique challenges for diagnosis and management. This review summarizes current approaches to diagnosis and management in FD/MAS, with emphasis on the clinical and therapeutic implications for the craniofacial skeleton.

Diagnostic value of MDM2 RNA in situ hybridization for low-grade osteosarcoma: Consistency comparison of RNA in situ hybridization, fluorescence in situ hybridization, and immunohistochemistry

Detection of MDM2 gene amplification via fluorescence in situ hybridization (FISH) and MDM2 overexpression by immunohistochemistry (IHC) have been utilized for the diagnosis of low-grade osteosarcoma (LGOS). The aim of this study was to evaluate the diagnostic value of MDM2 RNA in situ hybridization (RNA-ISH) and compare this assay with MDM2 FISH and IHC in distinguishing LGOS from its histologic mimics. MDM2 RNA-ISH, FISH and IHC were performed on nondecalcified samples of 23 LGOSs and 52 control cases. Twenty (20/21, 95.2%) LGOSs were MDM2-amplified, and two cases failed in FISH. All control cases were MDM2-nonamplified. All 20 MDM2-amplified LGOSs and one MDM2-nonamplified LGOS harboring TP53 mutation and RB1 deletion showed positivity for RNA-ISH. Fifty of the 52 (96.2%) control cases were negative for RNA-ISH. The diagnostic sensitivity and specificity of MDM2 RNA-ISH were 100.0% and 96.2%, respectively. Nineteen of the 23 LGOSs were evaluated by MDM2 RNA-ISH and FISH in decalcified samples simultaneously. All decalcified LGOSs failed in FISH and most samples (18/19) were no staining in RNA-ISH. Fifteen (15/20, 75%) MDM2-amplified LGOSs were positive for IHC and 96.2% (50/52) of control cases were negative. The sensitivity of RNA-ISH (100%) was higher than that of IHC (75%). In conclusion, MDM2 RNA-ISH has great value for the diagnosis of LGOS, with excellent consistency with FISH and better sensitivity than IHC. Acid decalcification still has an adverse impact on RNA. Some MDM2-nonamplified tumors may show positivity for MDM2 RNA-ISH, which needs to be analyzed comprehensively in combination with clinicopathological features.

Osteogenic sarcomas of the hands: A case series with emphasis in its peculiarities and literature review

AIM

To present our experience on osteosarcomas of the hands and review the existing literature pertaining osteosarcomas in this extremely rare location.

METHODS

and results: Seven cases of osteosarcomas of the hands were reviewed, and a literature search of all primary osteosarcomas of the hands was performed. All tumors occurred in adults (mean age, 41 years) and were located mainly around the metacarpophalangeal joints. All patients presented with localized long-lasting pain as main symptom. The mean size at diagnosis was 33 mm. Three tumors were low-grade central osteosarcomas, 1 low-grade central chondroblastoma-like osteosarcoma and 3 high-grade osteosarcomas. All tumors were positive for mouse double-minute 2 homolog (MDM2) immunohistochemistry. Three cases yielded results with fluorescence in-situ amplification for MDM2 (12q15)/CEP12. At last follow-up, one patient with a high-grade osteosarcoma was dead of disease. The literature review revealed similar demographic and site distribution of osteosarcomas within the hands than our series and an unusually high proportion of low-grade central and parosteal osteosarcomas when compared to the proportion of these infrequent neoplasms in the whole skeleton.

CONCLUSIONS

osteosarcomas of hands present in older individuals compared to the population affected by conventional osteosarcomas of all sites. Importantly from a diagnostic, therapeutic and prognostic points of view, around 40% of osteosarcomas of the hands are low-grade osteosarcomas of the central or parosteal types.

Temporal bone osteoblastoma involving temporomandibular joint diagnosed as simple disc disorders: A case report

Background

Osteoblastoma is quite rare in the oromaxillo-facial region, while the mandible is always the predilection. However, in our case, the lesion was located in the left temporal articular tubercle, involving the adjacent skull base, which is extremely rare in the literature.

Case reports

It had been diagnosed as the most common temporomandibular joint disorder in the local hospital before the patient came to our department, mainly due to the primary symptom, that was, the patient got pain in the left temporomandibular joint area while opening the mouth. However, we found a mass of bone lesions at the left temporal articular tubercle in MRI and cone beam CT, and it turned out to be an osteoblastoma after surgery. The patient's primary symptom disappeared after recovering from the surgery, and there have been no indications of complication or recurrence up to now.

Conclusion

Osteoblastoma is very rare in the temporomandibular joint region. It could easily miss the possibility of a benign tumor due to its unusual location and confusing chief complaint in this case. Our report provides experience in the identification of osteoblastoma in rare sites.

Dedifferentiated Low-Grade Osteosarcoma, Outcome with or Without Chemotherapy: A Systematic Review

The treatment of low-grade osteosarcomas is surgical resection with wide margins. In instances of dedifferentiation, a therapeutic paradigm similar to that of conventional high-grade osteosarcoma has not been adequately evaluated in these neoplasms. The main objective of this review was to define whether the addition of chemotherapy to surgical treatment has an impact on the survival of patients with dedifferentiated low-grade osteosarcomas. Secondary objectives were to observe the degree of histological response to neoadjuvant chemotherapy and to describe the percentage of de novo dedifferentiation. A systematic search of articles including dedifferentiated low-grade osteosarcomas, published between 1980 and 2022 was carried out in the PubMed, Cochrane and Scielo databases. A qualitative synthesis of the results was performed. Twenty-three articles comprising 117 patients were included. The survival of patients treated with surgery alone and surgery with chemotherapy was not statistically significant between the two groups. A good histological response was seen in 20% of specimens treated with neoadjuvant chemotherapy. De novo dedifferentiation was seen in approximately a fifth of low-grade osteosarcomas. The evidence available suggests that the addition of chemotherapy does not have an impact on the survival of patients with low-grade dedifferentiated osteosarcomas.

Intramedullary Well-differentiated Osteosarcoma: Imaging and Pathologic Findings in 17 Patients

BACKGROUND

Intramedullary well-differentiated osteosarcoma (IMWDOS) is rare and may easily be misdiagnosed.

OBJECTIVE

This study aimed at investigating the clinical, imaging, and pathological features of IMWDOS for correct diagnosis.

MATERIALS AND METHODS

Seventeen patients with IMWDOS were enrolled, and their clinical, imaging, and pathological data were analyzed.

RESULTS

Total 13 males and 4 females aged 19-55 years (mean 36. 1) were selected. The lesion was located at long bones in 16 patients and the second region of the acetabulum in one patient. Except for three patients with limited areas of lesions, all the other patients had a wide distribution of tumor, and the lesion in long bones involved the metaphysis area with possible extension towards the diaphysis. In imaging, the lesion usually had an unclear boundary with the destruction of bone cortex, uneven thickness of the bone cortex, thick and coarse trabecula in the lesion, but few periosteal reactions and soft tissue masses. The lesion was histologically composed of spindle cells with slight atypia. Follow-up was performed 2-101 months (mean 31.9m) in 14 cases, 10 years in one case, and 26 years in the remaining two. At follow-up, 12 patients (12/17 or 70.6%) who had a complete resection, including amputation (n=2), wide excision (n=8), and endoprosthetic replacement (n=2), showed no recurrence or metastasis. Among five patients who underwent curettage, three (3/17 or 17.6%) had recurrent lesions, leading to death in two of them, and the third one died during post-operation chemotherapy.

CONCLUSION

Intramedullary well-differentiated osteosarcoma tends to occur at the metaphysis of long bones, especially at the distal femur. Histological, clinical, and imaging findings lack specific characteristics and should be examined collectively to reach a correct diagnosis. The prognosis of patients with complete lesion resection is good, while incomplete lesion curettage or resection will lead to recurrence and transformation into a highly malignant tumor.

GRM1 Immunohistochemistry Distinguishes Chondromyxoid Fibroma From its Histologic Mimics

Chondromyxoid fibroma (CMF) is a rare benign bone neoplasm that manifests histologically as a lobular proliferation of stellate to spindle-shaped cells in a myxoid background, exhibiting morphologic overlap with other cartilaginous and myxoid tumors of bone. CMF is characterized by recurrent genetic rearrangements that place the glutamate receptor gene GRM1 under the regulatory control of a constitutively active promoter, leading to increased gene expression. Here, we explore the diagnostic utility of GRM1 immunohistochemistry as a surrogate marker for GRM1 rearrangement using a commercially available monoclonal antibody in a study of 230 tumors, including 30 CMF cases represented by 35 specimens. GRM1 was positive by immunohistochemistry in 97% of CMF specimens (34/35), exhibiting moderate to strong staining in more than 50% of neoplastic cells; staining was diffuse (>95% of cells) in 25 specimens (71%). Among the 9 CMF specimens with documented exposure to acid decalcification, 4 (44%) exhibited diffuse immunoreactivity (>95%) for GRM1, whereas all 15 CMF specimens (100%) with lack of exposure to decalcification reagents were diffusely immunoreactive ( P =0.003). High GRM1 expression at the RNA level was previously observed by quantitative reverse transcription polymerase chain reaction in 9 CMF cases that were also positive by immunohistochemistry; low GRM1 expression was observed by quantitative reverse transcription polymerase chain reaction in the single case of CMF that was negative by immunohistochemistry. GRM1 immunohistochemistry was negative (<5%) in histologic mimics of CMF, including conventional chondrosarcoma, enchondroma, chondroblastoma, clear cell chondrosarcoma, giant cell tumor of the bone, fibrous dysplasia, chondroblastic osteosarcoma, myoepithelial tumor, primary aneurysmal bone cyst, brown tumor, phosphaturic mesenchymal tumor, CMF-like osteosarcoma, and extraskeletal myxoid chondrosarcoma. These results indicate that GRM1 immunohistochemistry may have utility in distinguishing CMF from its histologic mimics.

Dedifferentiation in low-grade osteosarcoma: a Japanese Musculoskeletal Oncology Group (JMOG) study

BACKGROUND

Low-grade osteosarcomas, namely parosteal osteosarcoma (POS) and low-grade central osteosarcoma (LGCOS), occasionally dedifferentiate into high-grade malignancy, referred to as dedifferentiation in low-grade osteosarcoma (DLOS). This study aimed to elucidate the clinicopathologic features of DLOS, which are poorly described to date due to the extreme rarity of the disease.

METHODS

A total of 33 patients with DLOS were included. Clinical characteristics, including the diagnostic accuracy of tumor biopsy, multimodal treatments, and clinical course, were retrospectively reviewed. Univariate analysis was performed to identify prognostic factors associated with overall survival (OS) and metastasis-free survival (MFS).

RESULTS

The tumor subtypes comprised 10 cases (30.3%) of LGCOS and 23 cases (69.7%) of POS. The timing of dedifferentiation was synchronous in 25 (75.8%) and metachronous in 8 (24.2%) patients. The rates of preoperative diagnosis of DLOS were 40.0% and 65.4% for core needle biopsy and incisional biopsy, respectively. All patients underwent surgery and 25 patients received perioperative chemotherapy. Of the 13 patients who received neoadjuvant chemotherapy, 11 exhibited a poor histological response. The 5-year OS and MFS rates were 88.1% and 77.7%, respectively. Univariate analysis revealed that local recurrence was associated with poor OS (P < 0.01) and MFS (P < 0.01). Perioperative chemotherapy did not affect OS or MFS.

CONCLUSIONS

The diagnostic accuracy of tumor biopsy for DLOS was lower than that for bone sarcomas, as reported previously. In contrast to conventional osteosarcomas with high chemosensitivity, both histological responses and survival analysis revealed low efficacy of chemotherapy for DLOS.

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

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

Osteosarcoma of the Mandible in an Elderly Patient

Osteosarcoma is a malignant tumor in which the cancerous cells produce an osteoid matrix or mineralized bone. Jaw bones are affected in 6% of all osteosarcomas and are the fourth most common site of origin. Surgical treatment of osteosarcoma in elderly patients is rarely reported. Here, we report successful treatment of osteosarcoma arising in the mandible of a 90-year-old man. The patient was referred to our institution for diagnosis and treatment of an oral lesion. Intraoral examination revealed that a hard mass measuring 35 × 27 mm was located on the floor of the oral cavity, attached to the bone, and its growth displaced the tongue posteriorly. Therefore, he experienced difficulty in speech and swallowing. Biopsy of the mandibular mass was suspicious for chondrosarcoma. Preoperative examination did not detect critical risks for general anesthesia or surgery. Based on a clinical diagnosis of a malignant bone tumor of the mandible, segmental mandibular resection with reconstruction using a titanium plate was performed. Surgical site infection occurred on postoperative day 12, which was resolved by drainage, local irrigation, and administration of antibiotics. There was no delirium or cardiovascular or pulmonary complications. Surgery resolved the patient's difficulties in speech and swallowing. There was no evidence of tumor recurrence or metastasis 4 years after surgery. This case showed that it was not necessary to exclude surgical treatment merely because the patient was 90 years old. Indications for surgery should be determined individually to improve the patient's quality of life.

Role of MDM2, CDK4, BCL2, Parafibromin and Galectin 1 in Differentiating Osteosarcoma from its Benign Fibro-osseous Lesions

Benign fibro-osseous lesions (BFOLs) are a diverse group of lesions showing considerable degree of overlap with low grade osteosarcoma (LGOS). Further, de-differentiated osteosarcoma (DOS) is usually indistinguishable from conventional high-grade OS (COS) if LGOS foci are not identified. Thus, there is a need for adjunctive immunohistochemical markers to differentiate OS from benign FOLs as well as DOS from COS. This study evaluated the role of immunohistochemical expression of MDM2, CDK4, parafibromin, BCL-2 and Galectin-1 (Gal-1) in accurate characterization of benign FOLs and in differentiating them from OS. From our archives, we retrieved 101 tissue samples which were diagnosed as osteosarcoma (OS) /ossifying fibroma (OF) / fibrous dysplasia (FD) or fibrous hyperplasia (FH) and examined their immunohistochemical staining pattern with the aforementioned antibodies. MDM2 showed 100% specificity for diagnosing OS. CDK4 and Gal-1 showed linear increase in immunoexpression from benign BFOLs to OS. BCL-2 showed equivocal immunopositivity in OF and OS, but the positivity was higher than that observed in FD. The highest immunoexpression for parafibromin was seen in FD followed by OF and OS cases. Thus, MDM2 is most specific, and Gal-1 is most sensitive of all the markers studied in differentiating OS from benign mimics. Combination of these two markers can be used as an adjunct to conventional imaging and microscopy in accurate characterization of these lesions. Further MDM2 overexpression can differentiate DOS and COS.

Noncanonical roles of p53 in cancer stemness and their implications in sarcomas

Impairment of the prominent tumor suppressor p53, well known for its canonical role as the "guardian of the genome", is found in almost half of human cancers. More recently, p53 has been suggested to be a crucial regulator of stemness, orchestrating the differentiation of embryonal and adult stem cells, suppressing reprogramming into induced pluripotent stem cells, or inhibiting cancer stemness (i.e., cancer stem cells, CSCs), which underlies the development of therapy-resistant tumors. This review addresses these noncanonical roles of p53 and their implications in sarcoma initiation and progression. Indeed, dysregulation of p53 family proteins is a common event in sarcomas and is associated with poor survival. Additionally, emerging studies have demonstrated that loss of wild-type p53 activity hinders the terminal differentiation of mesenchymal stem cells and leads to the development of aggressive sarcomas. This review summarizes recent findings on the roles of aberrant p53 in sarcoma development and stemness and further describes therapeutic approaches to restore normal p53 activity as a promising anti-CSC strategy to treat refractory sarcomas.

Dedifferentiated Low-Grade Central Osteosarcoma of the Mandible

We present the first, to our knowledge, case of a dedifferentiated low-grade central osteosarcoma (LCOS) of the mandible. A 48-year-old Japanese woman underwent enucleation under general anesthesia after a diagnosis of ossifying fibroma. At the second recurrence, the pathological diagnosis after biopsy was of sarcoma with MDM2(+) and CDK4(+) immunohistochemical staining results. Hemimandibulotomy, supraomohyoid neck dissection, and free-flap reconstruction with a rectus abdominal flap were performed. A retrospective reevaluation of the first specimen with additional immunohistochemical staining for MDM2 and CDK4 yielded a final diagnosis of dedifferentiated LCOS. The patient showed no recurrence or lung metastasis 3 years after the final surgery.

Computed tomography and magnetic resonance imaging of an unusual intraconal orbital osteoma

We report the case of a 64-year-old male patient with a 5 month history of proptosis, motility limitation and vision loss in OD. Visual acuity (VA) was 20/200 in OD and 20/20 in OS. CT showed a large, round, intraconal lesion, with bony density and no apparent connection to adjacent orbital walls. MRI showed a T1-weighted hypointense lesion surrounded by a contrast enhancing capsule. The orbital tumor was excised through a lateral orbitotomy revealing a nodular, round, osseous structure. Histological examination disclosed well-formed lamellar bone trabeculae, with no necrosis or mitosis figures. Immunohistochemical staining was negative for MDM2 and CDK4. After 3 years, there was no evidence of tumor recurrence and VA had improved to 20/30. Intraconal osteomas with no clear attachment to orbital walls are extremely rare. We are aware of a few reported cases in the lid, hand, thigh, tongue, pterygopalatine fossa and brain. To the authors' knowledge, this is the first report in English literature of an orbital intraconal osteoma without any visible relation to the orbital walls.

Update of Key Clinical, Histological and Molecular Features of Malignant Bone Tumours Arising in the Craniofacial Skeleton

The craniofacial skeleton is a highly complex and specialized anatomic region containing and protecting the brain and sensory organs. Bone sarcomas arising here comprise a heterogeneous group of tumours, some of which differ in their biological behaviour compared to their peripheral counterparts. The reasons for this seem to lie, at least partially, in the embryonal development of the craniofacial bones. For reaching the correct diagnosis as the cornerstone of optimal personalised treatment planning, a multidisciplinary team of specialists, including pathologists, radiologists, oncologists, and head and neck surgeons needs to be involved. The most common tumours arising in the craniofacial bones are bone-forming tumours, cartilage-forming tumours, fibro-osseous lesions, giant cell-rich lesions, and notochordal tumours. While morphology remains the backbone for the diagnosis, the last decade has witnessed tremendous advances in the molecular characterization of tumours, and molecular testing is increasingly becoming a part of the diagnostic process. The integration of these new molecular markers into the diagnostic approach has undoubtedly increased the diagnostic accuracy and objectivity, and holds great promise to also identify new therapeutic targets for precision medicine in the future. Examples include HEY1-NCOA2 in mesenchymal chondrosarcoma, IDH1/2 mutations in chondrosarcoma and TFCP2 rearrangements in rhabdomyosarcoma. In this article, key clinical, histological and molecular features of malignant bone tumours arising in the craniofacial region are discussed, with a special focus on the differential diagnosis and prognostic considerations.

SATB2 and MDM2 Immunoexpression and Diagnostic Role in Primary Osteosarcomas of the Jaw

Primary osteosarcomas of the jaw (OSJ) are rare, accounting for 6% of all osteosarcomas. This study aims to determine the value of SATB2 and MDM2 immunohistochemistry (IHC) in differentiating OSJ from other jawbone mimickers, such as benign fibro-osseous lesions (BFOLs) of the jaw or Ewing sarcoma of the jaw. Certain subsets of osteosarcoma harbor a supernumerary ring and/or giant marker chromosomes with amplification of the 12q13-15 region, including the murine double-minute type 2 (MDM2) and cyclin-dependent kinase 4 (CDK4) genes. Special AT-rich sequence-binding protein 2 (SATB2) is an immunophenotypic marker for osteoblastic differentiation. Cases of OSJ, BFOLs (ossifying fibroma and fibrous dysplasia) of the jaw, and Ewing sarcoma of the jaw were retrieved from the Departments of Oral Pathology and Oral Medicine, Faculty of Dentistry, Obafemi Awolowo University and Lagos State University College of Medicine, Nigeria. All OSJ retrieved showed histologic features of high-grade osteosarcoma. IHC for SATB2 (clone EP281) and MDM2 (clone IF2), as well as fluorescence in situ hybridization (FISH) for MDM2 amplification, were performed on all cases. SATB2 was expressed in a strong intensity and diffuse staining pattern in all cases (11 OSJ, including a small-cell variant, 7 ossifying fibromas, and 5 fibrous dysplasias) except in Ewing sarcoma, where it was negative in neoplastic cells. MDM2 was expressed in a weak to moderate intensity and scattered focal to limited diffuse staining pattern in 27% (3/11) of cases of OSJ and negative in all BFOLs and the Ewing sarcoma. MDM2 amplification was negative by FISH in interpretable cases. In conclusion, the three cases of high-grade OSJs that expressed MDM2 may have undergone transformation from a low-grade osteosarcoma (LGOS). SATB2 is not a dependable diagnostic marker to differentiate OSJ from BFOLs of the jaw; however, it could serve as a valuable diagnostic marker in differentiating the small-cell variant of OSJ from Ewing sarcoma of the jaw, while MDM2 may be a useful diagnostic marker in differentiating OSJ from BFOLs of the jaw, especially in the case of an LGOS or high-grade transformed osteosarcoma.

Osteosarcoma: Old and New Challenges

Diagnosis of osteosarcoma can be challenging because of its diverse histological patterns and the lack of diagnostic biomarkers for most examples. This review summarizes the key pathologic findings of osteosarcoma subtypes (high-grade central, parosteal, low-grade central, periosteal, high-grade surface, and secondary) with an emphasis on describing and illustrating histological heterogeneity to help general pathologists. Differential diagnoses are listed for each entity, and histological subtype and distinguishing features, including molecular genetic findings (eg, MDM2, IDH, H3F3A, FOS, and USP6), are discussed. The review also covers recently established and emerging concepts and controversies regarding osteosarcoma.

Surface bone sarcomas: an update on current clinicopathological diagnosis and treatment

Surface bone sarcomas are rare malignant bone tumours. Osseous and cartilaginous surface bone sarcomas are the most common, with parosteal and periosteal osteosarcomas, periosteal chondrosarcomas and secondary peripheral chondrosarcomas being the most frequent.

Their clinical symptoms are non-specific and include pain for several months, swelling and limited range of motion of the adjacent joints.

Prompt diagnosis is important, as biological behaviour, imaging and histopathologic characteristics, treatment and prognosis differ considerably from their conventional intramedullary counterparts. Moreover, their imaging characteristics are not infrequently non-characteristic and may be misinterpreted as juxtacortical benign lesions leading to incorrect diagnosis and treatment, with life-threatening repercussions. Molecular studies and histopathological sampling are essential for accurate diagnosis.

There are still numerous issues regarding the biology, pathophysiology and treatment options of these entities due to their rarity.

Cite this article: EFORT Open Rev 2021;6:905-917. DOI: 10.1302/2058-5241.6.210064

Fibrous and Fibro-Osseous Lesions of Bone

Fibrous and fibro-osseous tumors are some of the most common benign lesions involving bones. Although many of the histomorphologic features of these tumors overlap significantly, an interdisciplinary approach helps to consolidate the classification of these tumors. Herein, the clinical, radiologic, and pathologic features of lesions within these categories are described.

Pathology of pleomorphic/undifferentiated and dedifferentiated bone neoplasms

Primary malignant bone tumors are uncommon and their accurate classification requires careful correlation of clinical, radiological, and pathologic findings. It is a heterogeneous group of tumors with a wide spectrum of morphology and their biological potential can be of low- or high-grade, depending on their risk for developing metastases. Over the past several decades, the classification of bone sarcomas has remained largely constant. However, some of the tumors have been reclassified and several new entities have emerged. In this review, we will focus on pleomorphic fibrosarcoma/UPS and dedifferentiated bone tumors, discuss their key diagnostic features, differential diagnosis, and their relation to prognosis.

Dedifferentiated Osteosarcoma of the Distal Ulna: A Case Report

Osteosarcoma is the most common malignant primary bone tumor that occurs most frequently in the second decade of life but rarely in patients over 40 years of age. The most common primary sites of osteosarcoma are the distal femur followed by proximal tibia and proximal humerus, and involvement of the wrist is extremely rare. Moreover, dedifferentiated osteosarcoma is also a rare condition that progresses to high-grade osteosarcoma from low-grade osteosarcoma, usually central low-grade osteosarcoma or parosteal osteosarcoma that bears MDM2 and/or CDK4 gene amplifications. We herein report an extremely rare case of dedifferentiated osteosarcoma arising in the distal ulna of an adult over 40 years of age. The patient was a 46-year-old man with a 2-month history of pain in his left swollen wrist. The initial radiological findings suggested a benign bone tumor in the distal ulna, and the lesion was marginally excised at the nearby hospital. Although the pathological diagnosis at the nearby hospital suggested a benign cartilaginous tumor, the tumor recurred in an aggressive manner 8 months after the initial surgery. The patient was referred to our hospital, and an incisional biopsy showed a high-grade osteosarcoma. The primary tumor was retrospectively re-evaluated at our hospital and diagnosed as low-grade osteosarcoma. Since neoadjuvant chemotherapy failed to shrink the tumor, the patient had to undergo below the elbow amputation to cure the disease. Although the tumor was negative for MDM2 nor CDK4, the definitive diagnosis of dedifferentiated osteosarcoma was made according to the clinical course and the histological findings. Lung metastases were found 10 months after the amputation, which were successfully treated by neoadjuvant chemotherapy and surgery. The patient has been doing well with no evidence of disease for 1 year and 6 months. Surprisingly, the literature review revealed that many low-grade osteosarcomas of the distal ulna progressed to high-grade dedifferentiated osteosarcomas. One should bear in mind that the diagnosis and treatment for bone-forming tumors of the distal ulna should be made very carefully because, although rare, it is possible that the tumor may initially appear as a benign or low-grade malignant tumor and may progress to high-grade osteosarcoma.

Juvenile psammomatoid ossifying fibroma of the parietal bone and review of calvarial presentations: illustrative case

BACKGROUND

Juvenile psammomatoid ossifying fibroma (JPOF) is an uncommon benign fibro-osseous lesion that only rarely presents in the calvaria.

OBSERVATIONS

The authors reported a case of JPOF in the left parietal bone of a 20-year-old patient and reviewed the 27 other cases of JPOF occurring in the calvaria as reported in the literature.

LESSONS

JPOF rarely presents in the calvaria, and because diagnosis is a histopathologic one, clinicians should consider this entity when presented with a lytic, expansile mass on imaging. Little is known about the molecular mechanisms driving development of JPOF. MDM2 amplification may play a role, although this was not seen in the case presented herein.

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

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

Ossifying Fibromas of the Head and Neck Region: A Clinicopathological Study of 45 Cases

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.

The importance of clinical and radiological findings for the definitive histopathologic diagnosis of benign fibro-osseous lesions of the jaws: Study of 276 cases

PURPOSE

Benign fibro-osseous lesions (BFOLs) are heterogeneous intraosseous disease processes sharing overlapping histopathologic features and demonstrate a wide range of biological behavior. The aim of this study is to highlight the importance of clinical and radiological findings for the definitive histopathologic diagnosis of benign fibro-osseous lesions of the jaws.

MATERIALS AND METHODS

This is a cross-sectional retrospective study evaluating the three main groups of BFOLs: Cemento-osseous dysplasia, ossifying fibromas, and fibrous dysplasia. Previously diagnosed BFOL cases were searched for thoroughly from the archives of Istanbul University, Institute of Oncology, Department of Tumor Pathology in between 2005 and 2015. Clinical and radiological data of these cases were identified and recorded. The histopathologic features were reevaluated from the H&E-stained slides.

RESULTS

A total of 276 BFOL cases were identified and reevaluated for the study. The most common BFOL type was cemento-osseous dysplasia (n = 135), followed by cemento-ossifying fibroma (n = 77), fibrous dysplasia (n = 53) and juvenile ossifying fibroma (n = 11). The female/male ratio was 3.4:1 with a strong predilection for the 4th decade (n = 102). The mandible (n = 209) was the predominantly affected jaw. Prominent osteoblastic rimming around the bony lesion was commonly observed for cemento-ossifying fibroma (n = 60/77), followed by cemento-osseous dysplasia (n = 23/135). Predominant ossification patterns showed some differences among the groups. The most common radiological feature was the mixed radiolucent/radiopaque internal structure.

CONCLUSION

Our results document various clinical, radiological and histopathologic findings of BFOLs. Even some histopathologic differences are observed, clinical and radiographic correlation is mandatory prior to the definitive histopathologic diagnosis of BFOLs for the prevention of possible misdiagnoses or inappropriate treatments.

MDM2 Amplified Sarcomas: A Literature Review

Murine Double Minute Clone 2, located at 12q15, is an oncogene that codes for an oncoprotein of which the association with p53 was discovered 30 years ago. The most important function of MDM2 is to control p53 activity; it is in fact the best documented negative regulator of p53. Mutations of the tumor suppressor gene p53 represent the most frequent genetic change in human cancers. By overexpressing MDM2, cancer cells have another means to block p53. The sarcomas in which MDM2 amplification is a hallmark are well-differentiated liposarcoma/atypical lipomatous tumor, dedifferentiated liposarcoma, intimal sarcoma, and low-grade osteosarcoma. The purpose of this review is to summarize the typical clinical, histopathological, immunohistochemical, and genetic features of these tumors.