Analysis of 12q13-15 genes in parosteal osteosarcoma

METTL1/WDR4-mediated tRNA m7G modification and mRNA translation control promote oncogenesis and doxorubicin resistance

Osteosarcoma is the most common bone tumor that leads to high mortality in adolescents and children. The tRNA N⁷-methylguanosine methyltransferase METTL1 is located in chromosome 12q14.1, a region that is frequently amplified in osteosarcoma patients, while its functions and underlying mechanisms in regulation of osteosarcoma remain unknown. Herein we show that METTL1 and WDR4 are overexpressed in osteosarcoma and associated with poor patient prognosis. Knockdown of METTL1 or WDR4 causes decreased tRNA m⁷G modification level and impairs osteosarcoma progression in vitro and in vivo. Conversely, METTL1/WDR4 overexpression promotes osteosarcoma proliferation, migration and invasion capacities. tRNA methylation and mRNA translation profiling indicate that METTL1/WDR4 modified tRNAs enhance translation of mRNAs with more m⁷G tRNA-decoded codons, including extracellular matrix (ECM) remodeling effectors, which facilitates osteosarcoma progression and chemoresistance to doxorubicin. Our study demonstrates METTL1/WDR4 mediated tRNA m⁷G modification plays crucial oncogenic functions to enhance osteosarcoma progression and chemoresistance to doxorubicin via alteration of oncogenic mRNA translation, suggesting METTL1 inhibition combined with chemotherapy is a promising strategy for treatment of osteosarcoma patients.

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.

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.

Clinical Utility of CDK4/6 Inhibitors in Sarcoma: Successes and Future Challenges

PURPOSE

Soft tissue and bone sarcomas are rare malignancies that exhibit significant pathologic and molecular heterogeneity. Deregulation of the CDKN2A-CCND-CDK4/6-retinoblastoma 1 (Rb) pathway is frequently observed in about 25% of unselected sarcomas and is pathognomonic for specific sarcoma subtypes. This genomic specificity has fueled the clinical evaluation of selective CDK4/6 inhibitors in sarcomas. Here, we highlight successes, opportunities, and future challenges for using CDK4/6 inhibitors to treat sarcoma.

MATERIALS AND METHODS

This review summarizes the current evidence for the use of CDK4/6 inhibitors in sarcoma while identifying molecular rationale and predictive biomarkers that provide the foundation for targeting the CDK4/6 pathway in sarcoma. A systematic review was performed of articles indexed in the PubMed database and the National Institutes of Health Clinical Trials Registry (ClinicalTrials.gov). For each sarcoma subtype, we discuss the preclinical rationale, case reports, and available clinical trials data.

RESULTS

Despite promising clinical outcomes in a subset of sarcomas, resistance to CDK4/6 inhibitors results in highly heterogeneous clinical outcomes. Current clinical data support the use of CDK4/6 inhibitors in subsets of sarcoma primarily driven by CDK4/6 deregulation. When dysregulation of the Rb pathway is a secondary driver of sarcoma, combination therapy with CDK4/6 inhibition may be an option. Developing strategies to identify responders and the mechanisms that drive resistance is important to maximize the clinical utility of these drugs in patients with sarcoma. Potential biomarkers that indicate CDK4/6 inhibitor sensitivity in sarcoma include CDK4, CCND, CCNE, RB1, E2F1, and CDKN2A.

CONCLUSION

CDK4/6 inhibitors represent a major breakthrough for targeted cancer treatment. CDK4/6 inhibitor use in sarcoma has led to limited, but significant, early clinical success. Targeted future clinical research will be key to unlocking the potential of CDK4/6 inhibition in sarcoma.

Response to CDK4/6-inhibitors in sarcomas indicate the need for predictive biomarkers specific to this disease.

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.

Parosteal osteosarcoma associated with a low-grade component mimicking well-differentiated liposarcoma: a case report

Parosteal osteosarcomas and well-differentiated liposarcomas are both well-differentiated locally aggressive tumors. They both have simple karyotypes with amplification of the 12q13-15 regions including MDM2 and CDK4 genes. In this report, we describe the case of a parosteal osteosarcoma intertwined with a low-grade component similar to a well-differentiated liposarcoma. The association of a bone component with an adipose component was initially overlooked. We describe the histological, imaging, and molecular characteristics of this tumor stressing the importance of radio-pathological correlation. To our knowledge, this is the second report of a parosteal osteoliposarcoma. Awareness of this rare presentation may allow radiologists and surgeons to recognize the peripheral fatty component as an integral part of the tumor.

The Utility of MDM2 and CDK4 Immunohistochemistry and MDM2 FISH in Craniofacial Osteosarcoma

Craniofacial osteosarcoma is rare (2-10% of all osteosarcomas). Most low grade fibroblastic osteosarcomas of the long bones are characterized by amplification of chromosome12q including MDM2 and CDK4 genes. This study aims to investigate the utility of MDM2 and CDK4 immunostains as well as MDM2 FISH in craniofacial osteosarcomas as a means of distinguishing them from benign fibro-osseous lesions. Cases of primary osteosarcoma and benign fibro-osseous lesions of the craniofacial bones were identified in the diagnostic pathology archives. MDM2 (SMP14 and/or IF2) and CDK4 (D9G3E and/or DCS-31) immunostains were performed on a representative block from each osteosarcoma and benign case. Fluorescence in situ hybridization (FISH) for MDM2 was performed on non-decalcified osteosarcomas. In osteosarcomas, the rate of expression of either MDM2 IF2, MDM2 SMP14, CDK4 DCS-31, or CDK4 D9G3E was 72.7% (8/11 cases), usually focal and weak. Using the MDM2 IF2 clone and the CDK4 DCS-31 clone, MDM2 and CDK4 were negative in lesional cells in all 14 benign fibro-osseous lesions. Using the IF2 and SMP14 clones, MDM2 nuclear expression was present in associated osteoclast-like giant cells in both benign and malignant cases. Of 4 successful cases, 1 high grade osteosarcoma was positive for MDM2 amplification. MDM2 or CDK4 expression or MDM2 amplification may aid in a diagnosis of head and neck osteosarcoma. However, when absent, sarcoma is not excluded. Due to focal weak expression of MDM2 in tumor cells in conjunction with nuclear expression in associated giant cells, caution should be exercised when interpreting positive stains.

[Parosteal low-grade osteosarcoma with focal differentiation]

This case study deals with the case of a 16-year-old male patient with a low-grade parosteal osteosarcoma of the distal femur with focal differentiation. Case history, disease course, and surgery as well as the pathological workup with final diagnosis are presented. Relevant radiologic and pathologic differential diagnoses und diagnostic pitfalls are explained in detail and discussed. Additionally, postoperative treatment options are illustrated.

Gene amplification and tumor grading in parosteal osteosarcoma

BACKGROUND

Parosteal osteosarcoma (POS) is a unique low grade osteosarcoma. Two separate oncogenes, MDM2 and CDK4, are specifically amplified in POS. Its clinical behavior is usually indolent. In some occasions, it may progress to high grade and become fatal. Malignant transformation with high grade differentiation is the most reliable indicator to predict its aggressiveness and metastatic potential. This study is to discover the relationship between gene amplification and grading.

METHODS

Retrospective analysis of MDM2/CDK4 expression/amplification using immunostaining, multiplex quantitative polymerase chain reaction (MQPCR) and fluorescence in situ hybridization (FISH) were studied on 14 patients with recurrent POS.

RESULTS

Forty tumor specimens in formalin-fixed paraffin-embedded blocks from 14 patients of POS were included in this study. Twenty-seven tumors are low-grade, 13 are high-grade. All POS showed increased expression of both MDM2 and CDK4 proteins, but not those from conventional osteosarcoma. Except some tumors were non-informative (poor DNA quality), the rest of POS had a marked increase of MDM2 and CDK4 genes copies by MQPCR, and confirmed by MDM2 FISH. Moreover, the folds of amplification increase as tumors progress. And, the amplification folds in high-grade POS are consistently higher than those of conventional ones.

CONCLUSION

FISH and MQPCR are both useful assays for estimating oncogene amplification status in bone tumors. Amplification levels of MDM2 and CDK4 are related to tumor grading and progression. Molecular determination of gene amplification status can be a reliable alternative for predicting clinical behavior of POS at small biopsies.

A clinical comparison between dedifferentiated low-grade osteosarcoma and conventional osteosarcoma

AIMS

The purpose of this study was to clarify the clinical behaviour, prognosis, and optimum treatment of dedifferentiated low-grade osteosarcoma (DLOS) diagnosed based on molecular pathology.

PATIENTS AND METHODS

We retrospectively reviewed 13 DLOS patients (six men, seven women; median age 32 years (interquartile range (IQR) 27 to 38)) diagnosed using the following criteria: the histological coexistence of low-grade and high-grade osteosarcoma components in the lesion, and positive immunohistochemistry of mouse double minute 2 homolog (MDM2) and cyclin-dependent kinase 4 (CDK4) associated with MDM2 amplification. These patients were then compared with 51 age-matched consecutive conventional osteosarcoma (COS) patients (33 men, 18 women; median age 25 years (IQR 20 to 38)) regarding their clinicopathological features.

RESULTS

The five-year overall survival (OAS) rates in the DLOS and COS patients were 85.7% and 77.1% (p = 0.728), respectively, and the five-year progression-free survival (PFS) rates were 57.7% and 44.9% (p = 0.368), respectively. A total of 12 DLOS patients received chemotherapy largely according to regimens for COS. Among the nine cases with a histological evaluation after chemotherapy, eight showed a poor response, and seven of these had a necrosis rate of < 50%. One DLOS patient developed local recurrence and five developed distant metastases.

CONCLUSION

Based on our study of 13 DLOS cases that were strictly defined by histological and molecular means, DLOS showed a poorer response to a standard chemotherapy regimen than COS, while the clinical outcomes were not markedly different. Cite this article: Bone Joint J 2019;101-B:745-752.

On the importance of considering disease subtypes: Earliest detection of a parosteal osteosarcoma? Differential diagnosis of an osteosarcoma in an Anglo-Saxon female

A case of potentially dedifferentiated parosteal osteosarcoma was found in the proximal humerus of an adult female buried in the late Anglo-Saxon cemetery of Cherry Hinton, Cambridgeshire, UK. Key features include a large, dense, lobulated mass attached to the medial metaphysis of the proximal humerus by a broad-based attachment, accompanied by cortical destruction and widespread spiculated periosteal reaction. Radiographic images confirm medullary involvement, lack of continuity between the cortex and external mass, a radiolucent cleavage plane and possible radiolucent zones within the bony masses. Differential diagnoses considered include osteochondroma, myositis ossificans, fracture callus, as well as the primary malignancies of osteosarcoma and chondrosarcoma, and their various subtypes. The macroscopic and radiographic analysis of the tumor is described and discussed within clinical and paleopathological contexts. One of only 19 uncontested examples of osteosarcoma from past human populations, most of which remain unconfirmed, this case represents what we believe to be the earliest, and probably singular, bioarcheological example of parosteal osteosarcoma in human history.

Clinical outcome of low-grade central osteosarcoma and role of CDK4 and MDM2 immunohistochemistry as a diagnostic adjunct

INTRODUCTION

Low-grade osteosarcoma encompasses parosteal osteosarcoma (POS) and low-grade central osteosarcoma (LCOS), with LCOS more rare than POS. LCOS is also more likely to be misdiagnosed and inappropriately treated with an intralesional procedure, due to its misleading radiological features and the overlap of its pathological characteristics with those of benign bone tumors. Therefore, as a diagnostic adjunct for LCOS, immunohistochemical assay with murine double-minute type 2 (MDM2) and cyclin-dependent kinase 4 (CDK4) have been tried with controversial results. We investigated (1) the clinical course and surgical outcome of LCOS, and (2) the diagnostic role of immune-histochemical markers (CDK4, MDM2) and their correlation with clinico-radiologic findings.

MATERIALS AND METHODS

We retrospectively reviewed 16 LCOS patients with regard to age, gender, tumor location, plain radiographic pattern, tumor volume, extraosseous extension, initial diagnosis, initial treatment, definitive diagnosis, definitive treatment, surgical margins, histochemical markers, and oncological outcome.

RESULTS

Final survival status was continuous disease-free in 14, alive with disease in 1, and remaining 1 patient died of other cancer. Except for 1 patient who had not undergone excision of their primary lesion, no patients developed a local recurrence. Eight tumors (50%) showed diffuse immunostaining for CDK4. Three of 8 tumors labeled for CDK4 were also positive for MDM2. Six (75%) of 8 CDK4-positive tumors displayed lytic lesions on a plain radiograph; in contrast, 2 (33%) of 6 tumors showing a sclerotic pattern on a plain radiograph were positive for CDK4.

CONCLUSIONS

The diagnosis of LCOS is challenging; however, if it is properly diagnosed, there is a high chance of a cure with wide excision alone. Positive immunostaining for CDK4 or MDM2 may be used as a diagnostic adjunct, although negative immunostaining cannot rule out this tumor. The clinical, radiological, and typical pathological findings are vital in raising the suspicion of this rare tumor.

MDM2 and CDK4 expression in periosteal osteosarcoma

Periosteal osteosarcoma is defined by the World Health Organization as an intermediate-grade, malignant, cartilaginous, and bone-forming neoplasm arising on the surface of bone. Unlike other subtypes of osteosarcoma, no data have been published about mouse double minute 2 (MDM2) and cyclin-dependent kinase 4 (CDK4) expression. For this reason, we evaluated the molecular and immunohistochemical features of MDM2 and CDK4 in 27 cases relative to 20 patients with a diagnosis of periosteal osteosarcoma, surgically treated at the Rizzoli Institute between 1981 and 2014. When possible, these results were compared with the MDM2 amplification status as determined by fluorescence in situ hybridization (FISH). All but 1 case (26/27, 96.3%) were negative for MDM2 protein using immunohistochemistry both in primary and in recurrent periosteal osteosarcoma, whereas gene amplification of MDM2 was not detected in any tumor analyzed (10 cases). The positive immunohistochemical case shows a weak/moderate focal nuclear expression of MDM2 antibody in the prevalent cartilaginous component and in the spindle cells of peripheral fibroblastic areas associated with osteoid production in a primary periosteal osteosarcoma. CDK4 immunohistochemical expression was negative in all 27 cases. This retrospective analysis has demonstrated that MDM2 and CDK4 are very rarely expressed in primary and recurrent periosteal osteosarcomas and therefore do not appear to be molecules central to the control of cancer development, growth, and progression in periosteal osteosarcoma. Therefore, when compared with low-grade central and parosteal osteosarcomas, MDM2 and CDK4 markers cannot be used diagnostically to differentiate this subtype of osteosarcoma.

Osteogenic tumors of bone

In this paper we provide an overview of benign and malignant osteogenic bone tumors. We describe the diagnostic features, radiographic findings, and pertinent ancillary studies needed to diagnose these bone-forming lesions. We begin with osteoid osteoma and osteoblastoma, which are histologically bland and eminently benign with rare possible exceptions. On the other end of the behavioral spectrum is osteosarcoma, which encompasses many subtypes ranging from high-grade osteogenic osteosarcoma to less overtly osteogenic lesions such as telangiectatic and small cell osteosarcoma. While classic osteogenic osteosarcoma can be easily recognized by its high grade morphology and formation of extracellular lace-like osteoid, its variants may pose diagnostic dilemmas as their differential diagnoses can include benign, fibrous, and vascular lesions, among others. Recognition of these variants is essential to avoid diagnostic pitfalls. In equivocal cases, some forms of osteosarcoma have shown molecular alterations that may prove diagnostically useful.

Sensitivity of MDM2 amplification and unexpected multiple faint alphoid 12 (alpha 12 satellite sequences) signals in atypical lipomatous tumor

This study assessed whether analysis of MDM2 copy number by fluorescence in situ hybridization (FISH) would help distinguish lipomas from atypical lipomatous tumors, otherwise referred to as well-differentiated liposarcomas, using a commercially available MDM2 FISH kit. 227 lipomatous and 201 non-lipomatous tumors were analyzed to assess its sensitivity and specificity. Of 178 mature lipomatous tumors, 86 were classified histologically as lipoma and 92 as atypical lipomatous tumor. Two of the lipomas harboring MDM2 amplification were reclassified as atypical lipomatous tumors. Overall, 13 atypical lipomatous tumors did not reveal MDM2 or CDK4 amplification, although this was reduced to 12 following analysis of multiple slides. Three of these cases revealed very occasional tumor cells harboring high-level MDM2 amplification, two had a dedifferentiated component, and MDM2 amplification was detected when one tumor recurred. The remaining six cases exhibited reactive/inflammatory features and were reclassified as lipomas. The findings indicate that MDM2 amplification is 93.5% sensitive for diagnosing atypical lipomatous tumor. A total of 2 of the 20 dedifferentiated liposarcomas failed to reveal MDM2 amplification. All atypical lipomatous tumors measured >10 cm, two dedifferentiated liposarcoma presented de novo at <10 cm, and ~50% of lipomas measured >10 cm. Spindle cell lipomas, lipoblastomas, hibernomas and pleomorphic liposarcomas did not reveal MDM2 amplification. Of 201 non-lipomatous tumors, eight revealed MDM2 amplification or multiple faint alphoid 12 signals and were reclassified as dedifferentiated liposarcoma. Multiple faint alphoid 12 signals were observed in nine tumors from seven patients, an observation not previously reported on paraffin sections: these included four atypical lipomatous tumors, and three dedifferentiated liposarcomas, one previously diagnosed as a myxofibrosarcoma, all of which also revealed amplification of CDK4, although two lacked MDM2 amplification. MDM2 FISH test is a useful adjunct to histology for distinguishing lipoma from atypical lipomatous tumor. The limitations of molecular genetic tests must be known before introducing them into a clinical service.

The genetics of osteosarcoma

Osteosarcoma is a primary bone malignancy with a particularly high incidence rate in children and adolescents relative to other age groups. The etiology of this often aggressive cancer is currently unknown, because complicated structural and numeric genomic rearrangements in cancer cells preclude understanding of tumour development. In addition, few consistent genetic changes that may indicate effective molecular therapeutic targets have been reported. However, high-resolution techniques continue to improve knowledge of distinct areas of the genome that are more commonly associated with osteosarcomas. Copy number gains at chromosomes 1p, 1q, 6p, 8q, and 17p as well as copy number losses at chromosomes 3q, 6q, 9, 10, 13, 17p, and 18q have been detected by numerous groups, but definitive oncogenes or tumour suppressor genes remain elusive with respect to many loci. In this paper, we examine studies of the genetics of osteosarcoma to comprehensively describe the heterogeneity and complexity of this cancer.

MDM2 and CDK4 immunohistochemical coexpression in high-grade osteosarcoma: correlation with a dedifferentiated subtype

Low-grade osteosarcomas comprise a distinct subset of osteosarcomas. They may occasionally dedifferentiate into high-grade tumors, typically in the form of high-grade osteosarcoma, which are histologically indistinguishable from conventional osteosarcomas. MDM2 and CDK4 are often amplified in low-grade osteosarcomas and their dedifferentiated counterparts, and the encoded proteins are accordingly overexpressed. As MDM2/CDK4 expression was reportedly rare in conventional osteosarcoma, we hypothesized that these markers may help separate dedifferentiated osteosarcoma from the conventional type. To test this, we performed MDM2 and CDK4 immunohistochemistry on 81 primary and 26 recurrent/metastatic high-grade osteosarcomas and correlated these data with the histology of the primary resection material, with particular attention to the potential presence of any coexisting low-grade osteosarcomatous components. MDM2 and CDK4 coexpression was identified in 7 cases, and on careful histologic review 6 of them were discovered to contain foci of coexisting low-grade elements. One case was a known dedifferentiated parosteal osteosarcoma, and the remaining 5 cases were newly identified dedifferentiated osteosarcomas in which the limited low-grade components were originally unrecognized. An additional 11 cases expressed either marker alone, whereas the remaining 89 cases were negative for both markers; no resection material from these 100 cases presented with a low-grade component. MDM2/CDK4 gene amplification status, determined by quantitative polymerase chain reaction in selected cases, was largely concordant with immunoexpression. Our data suggest that MDM2 and CDK4 coexpression in high-grade osteosarcomas is sensitive and specific to those that progressed from low-grade osteosarcomas, and immunohistochemistry may help identify this dedifferentiated subgroup to facilitate accurate subclassification.

Osteosarcoma: Differential Diagnostic Considerations

Accurate diagnosis of bone-forming tumors, including correct subclassification of osteogenic sarcoma is critical for determination of appropriate clinical management and prediction of patient outcome. The morphologic spectrum of osteogenic sarcoma is extensive, however, and its histologic mimics are numerous. This review focuses on the major differential diagnoses of the specific subtypes of osteosarcoma, presents summaries of various diagnoses, and provides tips to overcoming pitfalls in diagnosis.

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

Low-grade osteosarcoma is a rare malignancy that may be subdivided into two main subgroups on the basis of location in relation to the bone cortex, that is, parosteal osteosarcoma and low-grade central osteosarcoma. Their histological appearance is quite similar and characterized by spindle cell stroma with low-to-moderate cellularity and well-differentiated anastomosing bone trabeculae. Low-grade osteosarcomas have a simple genetic profile with supernumerary ring chromosomes comprising amplification of chromosome 12q13-15, including the cyclin-dependent kinase 4 (CDK4) and murine double-minute type 2 (MDM2) gene region. Low-grade osteosarcoma can be confused with fibrous and fibro-osseous lesions such as fibromatosis and fibrous dysplasia on radiological and histological findings. We investigated MDM2-CDK4 immunohistochemical expression in a series of 72 low-grade osteosarcomas and 107 fibrous or fibro-osseous lesions of the bone or paraosseous soft tissue. The MDM2-CDK4 amplification status of low-grade osteosarcoma was also evaluated by comparative genomic hybridization array in 18 cases, and the MDM2 amplification status was evaluated by fluorescence in situ hybridization or quantitative real-time polymerase chain reaction in 31 cases of benign fibrous and fibro-osseous lesions. MDM2-CDK4 immunostaining and MDM2 amplification by fluorescence in situ hybridization or quantitative real-time polymerase chain reaction were investigated in a control group of 23 cases of primary high-grade bone sarcoma, including 20 conventional high-grade osteosarcomas, two pleomorphic spindle cell sarcomas/malignant fibrous histiocytomas and one leiomyosarcoma. The results showed that MDM2 and/or CDK4 immunoreactivity was present in 89% of low-grade osteosarcoma specimens. All benign fibrous and fibro-osseous lesions and the tumors of the control group were negative for MDM2 and CDK4. These results were consistent with the MDM2 and CDK4 amplification results. In conclusion, immunohistochemical expression of MDM2 and CDK4 is specific and provides sensitive markers for the diagnosis of low-grade osteosarcomas, helping to differentiate them from benign fibrous and fibro-osseous lesions, particularly in cases with atypical radio-clinical presentation and/or limited biopsy samples.

Liposarcoma: molecular genetics and therapeutics

Sarcomas are a group of heterogeneous tumours with varying genetic basis. Cytogenetic abnormalities range from distinct genomic rearrangements such as pathognomonic translocation events and common chromosomal amplification or loss, to more complex rearrangements involving multiple chromosomes. The different subtypes of liposarcoma are spread across this spectrum and constitute an interesting tumour type for molecular review. This paper will outline molecular pathogenesis of the three main subtypes of liposarcoma: well-differentiated/dedifferentiated, myxoid/round cell, and pleomorphic liposarcoma. Both the molecular basis and future avenues for therapeutic intervention will be discussed.

Low-grade extraskeletal osteosarcoma of the chest wall: case report and review of literature

Background

Low-grade extraskeletal osteosarcomas (ESOS) are extremely rare.

Case presentation

We present the first case of low-grade ESOS of the chest wall, which occurred in a 30-year-old man. Because of initial misdiagnosis and patient's refusal of surgery, the diagnosis was done after a 4-year history of a slowly growing mass in soft tissues, leading to a huge (30-cm diameter) calcified mass locally extended over the left chest wall. Final diagnosis was helped by molecular analysis of MDM2 and CDK4 oncogenes. Unfortunately, at this time, no surgical treatment was possible due to loco-regional extension, and despite chemotherapy, the patient died one year after diagnosis, five years after the first symptoms.

Conclusion

We describe the clinical, radiological and bio-pathological features of this unique case, and review the literature concerning low-grade ESOS. Our case highlights the diagnostic difficulties for such very rare tumours and the interest of molecular analysis in ambiguous cases.

Well-differentiated liposarcoma with low-grade osteosarcomatous component: an underrecognized variant

Mature bone formation in well-differentiated liposarcoma and dedifferentiated liposarcoma has been described as a reactive or "metaplastic" change in most reports, and its neoplastic nature has not been widely appreciated. We herein describe 9 cases of well-differentiated/dedifferentiated liposarcoma with distinct areas of fibroosseous tissue histologically indistinguishable from low-grade osteosarcomas, that is, parosteal osteosarcoma or low-grade central osteosarcoma. The tumors affected middle-aged to elderly patients, and occurred in the retroperitoneum and deep soft tissue of the extremities without connection to the skeletal system. Grossly, all the tumors showed biphasic appearance with lipogenic and osteogenic area, the latter representing 5% to 50% of the total tumor volume. Histologically, the lipogenic component exhibited typical histology of well-differentiated liposarcoma, whereas the osteogenic area consisted of fibroosseous tissue with numerous mature neoplastic bone trabeculae largely lacking osteoblastic rimming, with intervening fascicles of spindle cell proliferation showing low nuclear grade. All samples were positive for MDM2 and/or CDK4 on immunohistochemical analysis; the antibodies stained many osteocytes, indicating that the bone is neoplastic rather than reactive. Three cases showed high-grade osteosarcomatous transformation juxtaposed to the low-grade osteosarcomatous component, reminiscent of the "dedifferentiation" phenomenon of skeletal low-grade osteosarcoma. Follow-up revealed local recurrence in 4 cases, but no distant metastases were documented. Recognition of this earlier underappreciated subtype of well-differentiated/dedifferentiated liposarcoma is important, because the fibroosseous component may seem so bland that it may be confused with benign metaplasia such as myositis ossificans, or conversely, the lipomatous component may be inconspicuous that it may be dismissed as normal fat, and such misinterpretation may potentially result in suboptimal treatment.

Immunohistochemical analysis of MDM2 and CDK4 distinguishes low-grade osteosarcoma from benign mimics

Parosteal osteosarcoma and low-grade central osteosarcoma are two types of low-grade osteosarcoma that show similar clinical behaviors, histological features, and genetic background (ie, amplified sequences of 12q13-15, including MDM2 and CDK4). Low-grade osteosarcoma is often confused with benign lesions, and ancillary techniques to enhance diagnostic accuracy have been awaited. This study explores the use of MDM2 and CDK4 immunohistochemistry for the histological diagnosis of low-grade osteosarcoma. We studied 23 cases of low-grade osteosarcoma from 21 patients (parosteal osteosarcoma (n=14), low-grade central osteosarcoma (n=9)) and 40 cases of benign histological mimics (myositis ossificans (n=11), fibrous dysplasia (n=14), osteochondroma (n=6), desmoplastic fibroma (n=1), florid reactive periostitis (n=4), Nora's lesion (n=3), and turret exostosis (n=1)). Low-grade osteosarcoma labeled for MDM2 in 16 cases (70%) and for CDK4 in 20 cases (87%). All low-grade osteosarcomas expressed one or both markers (100%), with 13 cases (57%) expressing both. Staining pattern was diffuse in most cases, and the majority expressed moderate or strong intensity for either antibody. MDM2/CDK4 immunostaining was shown irrespective of low-grade osteosarcoma histological subtype. In contrast, only 1 Nora's lesion out of the 40 miscellaneous benign processes showed immunoreactivity for MDM2 or CDK4. The combination of these two markers thus shows 100% sensitivity and 97.5% specificity for the diagnosis of low-grade osteosarcoma. MDM2 and CDK4 immunostains therefore reliably distinguish low-grade osteosarcoma from benign histological mimics, and their combination may serve as a useful adjunct in this difficult differential diagnosis.

Characterization of the 12q15 MDM2 and 12q13-14 CDK4 amplicons and clinical correlations in osteosarcoma

The chromosomal region 12q13-15 is recurrently amplified in osteosarcoma (OS), but its importance in bone tumor development remains unknown. Although there are two major candidate genes (MDM2, a TP53 downregulator, and CDK4, involved in cell cycle progression) considered to be the driving genes in this region, the size of the amplicon and number of genes involved have not been determined. In this study, we used 130 classical OS and 15 parosteal OS to determine MDM2 and CDK4 amplification frequency in OS. Tumors in which these genes were amplified were used to map the 12q13-15 amplified region and to determine its correlation with clinical prognosis. The 12q13-15 amplification was more prevalent in parosteal OS (67% of cases) than in high-grade classical OS (12%). Quantitative real-time PCR of MDM2, CDK4, and 25 other genes showed that this region contains two different amplicons: one at 12q15 centered on MDM2 and one at 12q13-14 centered on CDK4. Both regions were frequently co-amplified in both types of OS, and MDM2 and CDK4 amplification was correlated with higher expression levels for both genes. Univariate and multivariate analyses of clinical data indicated that classical OS patients whose tumors exhibited MDM2 amplification were more likely to be older at diagnosis (median age 32.6 vs. 17.8 years) and female (66.7 vs. 33.3%) than those without gene amplification. There was no association with other clinical parameters. In conclusion, co-amplification of MDM2 and CDK4 in two separate amplicons occurs frequently in parosteal OS and less so in classical high-grade OS.

Dedifferentiated Liposarcomas With Divergent Myosarcomatous Differentiation Developed in the Internal Trunk

Dedifferentiated liposarcoma (DLPS) is one of the most frequent sarcomas of the retroperitoneum and represents most undifferentiated sarcomas of the internal trunk. In about 5% cases, the dedifferentiated component is an heterologous sarcoma such as leiomyosarcoma or rhabdomyosarcoma. We reviewed a series of 65 sarcomas with a myogenic differentiation developed in the internal trunk for which initial diagnoses were leiomyosarcoma (37), rhabdomyosarcoma (6), malignant mesenchymoma (6), and DLPS (16). Immunostainings for MDM2, CDK4, alpha smooth actin, desmin, caldesmon, myogenin, c-kit, and progesterone receptor were performed. In 48 cases, the amplification status of MDM2 and CDK4 could be evaluated with quantitative polymerase chain reaction on paraffin-embedded tissues extracted DNAs. After review of the cases, final diagnoses were leiomyosarcoma (35), rhabdomyosarcomatous (20) or leiomyosarcomatous (7) DLPS, probable DLPS (2), and malignant mesenchymoma (1). DLPS were bigger tumors (median: 18.2 cm) than leiomyosarcomas (median: 12 cm). They had a lower 5-year recurrence-free survival than leiomyosarcomas (45% vs. 71%) but a higher 5-year metastasis-free survival (73% vs. 39%). There was no significant difference in overall survival (57% vs. 34%). Outcome of patients with a DLPS with a myosarcomatous component did not differ from conventional DLPS. In conclusion, most sarcomas with a rhabdomyosarcomatous differentiation occurring in the internal trunk of adults are DLPS. Moreover, DLPS with a myogenic component have a low metastatic potential, similar to conventional DLPS and significantly lower to the metastatic potential of leiomyosarcomas.

Genomic profiling of bone and soft tissue tumors with supernumerary ring chromosomes using tiling resolution bacterial artificial chromosome microarrays

Ring chromosomes and/or giant marker chromosomes have been observed in a variety of human tumor types, but they are particularly common in a subgroup of mesenchymal tumors of low-grade or borderline malignancy. These rings and markers have been shown to contain amplified material predominantly from 12q13-15, but also sequences from other chromosomes. Such amplified sequences were mapped in detail by genome-wide array comparative genomic hybridization in ring-containing tumor samples from soft tissue (n = 15) and bone (n = 6), using tiling resolution microarrays, encompassing 32 433 bacterial artificial chromosome clones. The DNA copy number profiles revealed multiple amplification targets, in many cases highly discontinuous, leading to delineation of large numbers of very small amplicons. A total number of 356 (median size: 0.64 Mb) amplicons were seen in the soft tissue tumors and 90 (median size: 1.19 Mb) in the bone tumors. Notably, more than 40% of all amplicons in both soft tissue and bone tumors were mapped to chromosome 12, and at least one of the previously reported recurrent amplifications in 12q13.3-14.1 and 12q15.1, including SAS and CDK4, and MDM2, respectively, were present in 85% of the soft tissue tumors and in all of the bone tumors. Although chromosome 12 was the only chromosome displaying recurrent amplification in the bone tumors, the soft tissue tumors frequently showed recurrent amplicons mapping to other chromosomes, that is, 1p32, 1q23-24, 3p11-12, 6q24-25 and 20q11-12. Of particular interest, amplicons containing genes involved in the c-jun NH2-terminal kinase/mitogen-activated protein kinase pathway, that is, JUN in 1p32 and MAP3K7IP2 (TAB2) in 6q24-25, were found to be independently amplified in eight of 11 cases with 12q amplification, providing strong support for the notion that aberrant expression of this pathway is an important step in the dedifferentiation of liposarcomas.

MDM2 and CDK4 Immunostainings Are Useful Adjuncts in Diagnosing Well-Differentiated and Dedifferentiated Liposarcoma Subtypes

Atypical lipomatous tumor/well-differentiated liposarcoma (ALT-WDLPS) and dedifferentiated liposarcoma (DDLPS) may be difficult to distinguish from benign adipose tumors and from poorly differentiated sarcomas, respectively. Genetically, they are characterized by amplification of MDM2 and CDK4 genes on chromosome 12q13-15. We examined a series of 559 soft tissue tumors (44 ALT-WDLPS, 61 DDLPS, 49 benign adipose tumors, and 405 non-ALT-WDLPS/DDLPS sarcomas) for MDM2 and CDK4 expression using immunohistochemistry. MDM2 and CDK4 immunoexpressions were compared with gene amplification status (as assessed by quantitative PCR and/or comparative genomic hybridization) in 241 neoplasms. Most ALT-WDLPS/DDLPS expressed MDM2 (97%) and CDK4 (92%) as opposed to few benign adipose tumors (MDM2, 5%; CDK4, 2%) and a limited number of non-ALT-WDLSP/DDLPS sarcomas (MDM2, 19%; CDK4, 6%). The sensitivity and specificity of MDM2 and CDK4 immunostainings in identifying ALT-WDLPS/DDLPS among other soft tissue tumors were 97% and 92%, and 83% and 95%, respectively. MDM2 and CDK4 immunostainings were particularly useful to separate ALT-WDLPS from the large group of differentiated adipose tumors, and to distinguish DDLPS from poorly differentiated sarcomas. A strong correlation was observed between MDM2 and CDK4 stainings and gene amplification status. In conclusion, MDM2 and CDK4 immunostainings, which correlate with gene amplification, are helpful adjuncts to differentiate ALT-WDLPS from benign adipose tumors and to separate DDLPS from poorly differentiated sarcomas.

Dedifferentiated parosteal osteosarcoma: The experience of the Rizzoli Institute

BACKGROUND

Dedifferentiated parosteal osteosarcoma (DPOS) is a variant of osteosarcoma in which a high-grade sarcoma coexists with a conventional parosteal osteosarcoma (c-POS), either at presentation (synchronous type) or at the time of recurrence (metachronous type). Only approximately 60 patients have been reported in the literature. The objective of this study was to analyze the clinicopathologic and radiographic features of a relatively large number of patients with DPOS in an attempt to define further the histologic and biologic behavior of this rare entity.

METHODS

In a series of 120 patients with parosteal osteosarcoma who were seen at the Rizzoli Institute from 1958 to 2000, the authors identified 29 patients who were diagnosed with DPOS. The authors reviewed the clinical and radiologic features, histologic sections, treatments, and outcomes in this group of patients with DPOS.

RESULTS

Twelve patients were male, and 17 patients were female. The patients ranged in age from 15 years to 65 yrs (average, 36 years; median, 32 years). One tumor involved the scapula, one involved the ilium, and another involved the skull. All 26 of the other tumors were located in the long bones (14 in the femur, 5 in the humerus, 3 in the tibia, 3 in the fibula, and 1 in the ulna). In 18 patients, radiographic areas of lucency were seen within an otherwise sclerotic lesion. Histologically, the dedifferentiated component was high-grade osteoblastic osteosarcoma in 14 patients, fibroblastic osteosarcoma in 10 patients, giant cell-rich osteosarcoma in 3 patients, and chondroblastic osteosarcoma in 2 patients. All tumors were Stage IIB, and invasion of the medullary canal was detected in 19 patients (65%). Twenty-eight patients underwent surgery, and 18 of those patients received chemotherapy (5 patients received neoadjuvant chemotherapy, and 13 patients received adjuvant). Nine patients were dead and 20 patients were alive (average follow-up, 107 months; range, from 3 months to 36 years) at the last follow-up. Of the nine patients who died, one patient received no treatment, five patients underwent surgery (with three patients achieving adequate margins) in combination with chemotherapy, and three patients underwent surgery only (with adequate margins achieved). Of the 20 patients who remained alive, 13 patients underwent surgery (with 10 patients achieving adequate margins) in combination with chemotherapy, whereas 7 patients underwent surgery only (all with adequate margins). Seven of the nine patients who died had widespread metastases. One patient died of causes unrelated to the tumor, and another patient died shortly after undergoing resection of a lesion in the skull.

CONCLUSIONS

Dedifferentiation occurred in approximately 24% of patients with c-POS. The prognosis for patients with DPOS was better than the prognosis for patients with dedifferentiated central and dedifferentiated peripheral chondrosarcoma.

Clinicopathological and immunohistochemical analysis of twenty-five head and neck osteosarcomas

The aim of this study was to analyze the clinicopathological features and immunohistochemical expression of p53, MDM2, CDK4, PCNA and Ki67 proteins in 25 head and neck osteosarcomas registered in a single institution. The mean age of the patients was 29 years and the most common site was the mandible (60%). The predominant histological type was the chondroblastic (72%) and 52% of the cases were classified as intermediate-grade of malignancy. The immunohistochemical analysis displayed positivity in 52% of the cases for p53, 24% for MDM2, 84% for CDK4, 92% for PCNA and 88% for Ki-67. The majority of cases were treated with surgery alone or associated with chemotherapy. Five patients developed local recurrences, four had distant metastasis and six had persistent disease after initial treatment. The overall 5-year and 10-year survival rates were 59% and 49%, respectively, and the most important prognostic factors were prior history of radiation exposure and osteoblastic histological type.

Amplification pattern of 12q13-q15 genes (MDM2, CDK4, GLI) in urinary bladder cancer

The chromosomal region 12q13-q15 is recurrently amplified in bladder cancer. Putative target genes located in this region include MDM2, CDK4, and GLI. To evaluate the involvement of these genes in bladder cancer, we screened a tissue microarray (TMA) containing 2317 samples by fluorescence in situ hybridization (FISH). Amplification was found for MDM2 in 5.1%, for CDK4 in 1.1%, and for GLI in 0.4% of interpretable tumors. Among tumors having amplification of at least one of these 12q13-q15 genes, 76.6% had amplification of MDM2 alone and 6.4% had amplification of CDK4 alone. Coamplifications were seen of MDM2 and CDK4 in 10.6%, and of CDK4 and GLI in 6.4%. Neither coamplifications of all three genes nor isolated GLI amplifications were found. These data suggest a prominent role of MDM2 as a 12q13-q15 amplification target in bladder cancer. However, independent CDK4 amplifications do also occur suggesting either two non-overlapping amplification sites or else a minimal overlapping region between MDM2 and CDK4 perhaps containing another yet unknown oncogene. The frequency of amplification increased significantly from stage pTa to pT1-4 (P<0.04) and from low to high grade (P<0.005). These data are consistent with a high level of genetic instability in invasively growing and high-grade bladder tumors.

Differentially amplified chromosome 12 sequences in low- and high-grade osteosarcoma

Most osteosarcomas are highly aggressive malignancies characterized by a complex pattern of chromosome abnormalities. However, a subgroup of low-grade, parosteal tumors exhibits a relatively simple aberration pattern dominated by ring chromosomes carrying amplified material from chromosome 12. To assess whether sequences from this chromosome were differentially amplified in low- and high-grade osteosarcomas, copy numbers of the CCND2, ETV6, KRAS2, and D12S85 regions in 12p and the MDM2 region in 12q were evaluated by interphase or metaphase fluorescence in situ hybridization (FISH) in 24 osteosarcomas. Amplification of MDM2 was detected in all five low-grade and four high-grade osteosarcomas, all of which showed ring chromosomes. An overrepresentation of 12p sequences was found in 1/5 low-grade and in 9/19 high-grade tumors. Multicolor single-copy FISH analysis of metaphase cells from six high-grade tumors showed that extra 12p material either occurred together with MDM2 in ring chromosomes or was scattered over the genome as a result of complex structural rearrangements. Most tumors (8/10) not containing amplification of the assessed chromosome 12 loci exhibited a nondiploid pattern at evaluation with probes for centromeric alpha satellite sequences. These findings indicate that gain of sequences from the short arm of chromosome 12 could be a possible genetic pathway in the development of aggressive osteosarcoma.