Frequent IDH1/2 mutations in intracranial chondrosarcoma: a possible diagnostic clue for its differentiation from chordoma

Integrated Molecular and Histological Insights for Targeted Therapies in Mesenchymal Sinonasal Tract Tumors

PURPOSE OF REVIEW

This review aims to provide a comprehensive overview of mesenchymal sinonasal tract tumors (STTs), a distinct subset of STTs. Despite their rarity, mesenchymal STTs represent a unique clinical challenge, characterized by their rarity, often slow progression, and frequently subtle or overlooked symptoms. The complex anatomy of the sinonasal area, which includes critical structures such as the orbit, brain, and cranial nerves, further complicates surgical treatment options. This underscores an urgent need for more advanced and specialized therapeutic approaches.

RECENT FINDINGS

Advancements in molecular diagnostics, particularly in next-generation sequencing, have significantly enhanced our understanding of STTs. Consequently, the World Health Organization has updated its tumor classification to better reflect the distinct histological and molecular profiles of these tumors, as well as to categorize mesenchymal STTs with greater accuracy. The growing understanding of the molecular characteristics of mesenchymal STTs opens new possibilities for targeted therapeutic interventions, marking a significant shift in treatment paradigms. This review article concentrates on mesenchymal STTs, specifically addressing sinonasal tract angiofibroma, sinonasal glomangiopericytoma, biphenotypic sinonasal sarcoma, and skull base chordoma. These entities are marked by unique histopathological and molecular features, which challenge conventional treatment approaches and simultaneously open avenues for novel targeted therapies. Our discussion is geared towards delineating the molecular underpinnings of mesenchymal STTs, with the objective of enhancing therapeutic strategies and addressing the existing shortcomings in the management of these intricate tumors.

SMARCB1-Deficient Skull Base Chondrosarcoma with 12p Duplication Presenting as Somatic-Type Malignancy Arising from Metastatic Seminoma

Somatic-type malignancy (STM) can occur infrequently within a primary or metastatic testicular germ cell tumor (TGCT) and is associated with dismal prognosis and survival. STM with chondrosarcomatous features is exceedingly rare and head and neck involvement has not been previously documented. A 39-year-old white man presented with nasal obstruction and epistaxis. Imaging disclosed a 6.9-cm expansile tumor involving the nasal cavity and skull base with intraorbital and intracranial extension. The histopathologic properties of the tumor were compatible with chondrosarcoma, grade II-III. Immunohistochemically, malignant cells were strongly and diffusely positive for S100 and epithelial markers, and showed loss of SMARCB1 expression. IDH1/2 mutations were not detected. Following whole-body PET scan, a 7.0-cm left testicular mass was discovered and diagnosed as seminoma with syncytiotrophoblastic cells, stage pT3NXM1b. Extensive retroperitoneal, mediastinal, and supraclavicular lymphadenopathy was also noticed. Histopathologic examination of the left supraclavicular lymph node revealed metastatic seminoma. By FISH, most metastatic nodal seminoma cells harbored 1 to 4 copies of isochromosome 12p, while the chondrosarcoma featured duplication of 12p. Presence of a malignant TGCT with disseminated supradiaphragmatic lymphadenopathy, the unique immunophenotypic properties of the skull-based chondrosarcoma and lack of IDH1/2 aberrations with gain of 12p strongly support the diagnosis of STM chondrosarcoma arising from metastatic TGCT. The patient did not respond to chemotherapy and succumbed three months after diagnosis. Although exceedingly uncommon, metastasis to the head and neck may occur in patients with TGCT. This case of STM chondrosarcoma demonstrated divergent immunophenotypic and molecular characteristics compared to "typical" examples of head and neck chondrosarcoma. High index of suspicion is advised regarding the diagnosis of lesions that present with otherwise typical histomorphology but unexpected immunohistochemical or molecular features.

Diagnostics of IDH1/2 Mutations in Intracranial Chondroid Tumors: Comparison of Molecular Genetic Methods and Immunohistochemistry

Intracranial chondroid tumors are a heterogeneous group of neoplasms characterized by the presence of a cartilage matrix. These tumors exhibit overlapping clinical and histological features. Mutations in IDH1/2 genes serve as important diagnostic markers of tumor type, particularly chondrosarcoma. To improve the accuracy of IDH1/2 diagnostics, we compared three methods: biochip assay, real-time PCR with DNA melting analysis using TaqMan probes and sequencing (qPCR-DMA-Sanger), and immunohistochemistry (IHC). Tumor samples from 96 patients were investigated. The IDH1 mutations were detected in 34/64 (53%) chondrosarcomas; IHC detected 27/56 (48.2%) mutations, the qPCR-DMA-Sanger method 27/59 (46%) mutations, and the biochip assay revealed 29/60 (48.3%) mutations. The detection of IDH1 mutations in chordoma (2/15) and osteosarcoma (2/7) suggested the need for a revised diagnosis. In benign tumors, IDH1 mutations were present in chondroma (4/6), but absent in chondromyxoid fibroma (0/4). The most frequent IDH1 mutations were R132C (60%), R132L, and R132G (13.5% each), R132H (8%), and R132S (5%). The concordance between the biochip assay and IHC was 90%, between IHC and PCR-DMA-Sanger 83%, and between biochip assay and qPCR-DMA-Sanger was 98%, respectively. No IDH2 mutations were found. The use of independent diagnostic methods may improve the detection of IDH-mutant specimens in chondroid tumors.

Chordoma: demographics and survival analysis with a focus on racial disparities and the role of surgery, a U.S. population-based study

BACKGROUND

Chordoma is a rare malignant tumor of notochordal origin that may appear anywhere in the axial skeleton from the skull base to the sacrum. This study presents findings from a large database query to highlight the demographic, clinical, and pathological factors, prognosis, and survival of chordomas.

METHODS

The Surveillance, Epidemiology, and End Results (SEER) data based was used to identify patients with a "chordoma" diagnosis from 200 to 2018.

RESULTS

In a total of 1600 cases, the mean age at diagnosis was 54.47 years (standard deviation, SD ± 19.62 years). Most cases were male (57.1%) and white (84.5%). Tumor size was found to be > 4 cm in 26% of cases. Histologically, 33% with known features had well-differentiated Grade I tumors, and 50.2% of the tumors were localized. Metastasis at the time of to the bone, liver, and lung was observed at a rate of 0.5%, 0.1%, and 0.7%, respectively. The most common treatment received was surgical resection (41.3%). The overall 5-year overall survival observed was 39% (confidence interval, CI 95% 37-41; p = 0.05) with patients who received surgery having a 5-year survival rate of 43% (CI 95% 40-46; p = 0.05). Multivariate analysis showed independent factors that contributed to worse prognosis chemotherapy only as a treatment modality and no surgery as a treatment modality.

CONCLUSION

Chordomas are more common in white males and appear between the 5th and 6th decades of life. Factors that contributed to a worse prognosis were Asian, Pacific Islander, American Indian, or Alaska Native races.

Supratentorial multifocal gliomas associated with Ollier disease harboring IDH1 R132H mutation: A case report

Somatic mosaicism of isocitrate dehydrogenase 1/2 (IDH1/2) mutation is a cause of Ollier disease (OD), characterized by multiple enchondromatosis. A 35-year-old woman who was diagnosed with OD at age 24 underwent resection surgery for multifocal tumors located at the right and left frontal lobes that were discovered incidentally. No apparent spatial connection was observed on preoperative magnetic resonance imaging. Pathological examinations revealed tumor cells with a perinuclear halo in the left frontal lobe tumor, whereas astrocytic tumor cells were observed in the right frontal lobe tumor. Based on positive IDH1 R132H immunostaining and the result of 1p/19q fluorescent in situ hybridization, pathological diagnoses were IDH mutant and 1p/19q-codeleted oligodendroglioma in the right frontal lobe tumor and IDH mutant astrocytoma in the left frontal lobe tumor, respectively. The DNA sequencing revealed IDH1 R132H mutation in the peripheral blood sample and frontal lobe tumors. This case suggested that in patients with OD, astrocytoma and oligodendroglioma can co-occur within the same individual simultaneously, and IDH1 R132H mutation was associated with supratentorial development of gliomas.

Mutant IDH in Gliomas: Role in Cancer and Treatment Options

Altered metabolism is a common feature of many cancers and, in some cases, is a consequence of mutation in metabolic genes, such as the ones involved in the TCA cycle. Isocitrate dehydrogenase (IDH) is mutated in many gliomas and other cancers. Physiologically, IDH converts isocitrate to α-ketoglutarate (α-KG), but when mutated, IDH reduces α-KG to D2-hydroxyglutarate (D2-HG). D2-HG accumulates at elevated levels in IDH mutant tumours, and in the last decade, a massive effort has been made to develop small inhibitors targeting mutant IDH. In this review, we summarise the current knowledge about the cellular and molecular consequences of IDH mutations and the therapeutic approaches developed to target IDH mutant tumours, focusing on gliomas.

Malignant Brain and Spinal Tumors Originating from Bone or Cartilage

Malignant bone tumors affecting the brain and spine are a rare and exceedingly difficult-to-treat group of diseases. Most commonly consisting of chordoma and chondrosarcoma, these tumors also include giant-cell tumors and osteosarcomas. This chapter will cover the background, epidemiology, genetics, molecular biology, histopathology, radiographic features, clinical manifestations, therapeutic approaches, and clinical management of each entity.

SOX9 and SATB2 Immunohistochemistry Cannot Reliably Distinguish Between Osteosarcoma and Chondrosarcoma on Biopsy Material

INTRODUCTION

Limited tissue in biopsies of malignant bone lesions can preclude definitive subclassification, especially when cellular or matrix elements are sparse, absent, or confounding. It is uncertain whether IHC for SOX9 (marker of chondrogenesis) and SATB2 (marker of osteoblastic differentiation) may be discriminatory tools towards osteosarcoma and chondrosarcoma.

METHODS

This study interrogated the pre-resection biopsies of a cohort of osteosarcoma and chondrosarcoma with SATB2 and SOX9 in tandem, to assess their value as diagnostic adjuncts as well as their concordance with final resection diagnoses.

RESULTS

SATB2 was expressed more frequently in osteosarcoma (46/53, 86%) compared to chondrosarcoma (9/18, 50%); SOX9 was expressed in high frequencies in both osteosarcoma (52/53, 98%) and chondrosarcoma (17/18, 94%), and SATB2 and SOX9 were co-expressed in both osteosarcoma (46/53, 89%) and chondrosarcoma (8/18, 44%).

CONCLUSIONS

There exists significant overlap in expression of SATB2 and SOX9 in osteosarcoma and chondrosarcoma. These markers are not expressed in a distribution that is unique enough for application towards this particular diagnostic differential.

Metabolic adaptations in cancers expressing isocitrate dehydrogenase mutations

The most frequently mutated metabolic genes in human cancer are those encoding the enzymes isocitrate dehydrogenase 1 (IDH1) and IDH2; these mutations have so far been identified in more than 20 tumor types. Since IDH mutations were first reported in glioma over a decade ago, extensive research has revealed their association with altered cellular processes. Mutations in IDH lead to a change in enzyme function, enabling efficient conversion of 2-oxoglutarate to R-2-hydroxyglutarate (R-2-HG). It is proposed that elevated cellular R-2-HG inhibits enzymes that regulate transcription and metabolism, subsequently affecting nuclear, cytoplasmic, and mitochondrial biochemistry. The significance of these biochemical changes for tumorigenesis and potential for therapeutic exploitation remains unclear. Here we comprehensively review reported direct and indirect metabolic changes linked to IDH mutations and discuss their clinical significance. We also review the metabolic effects of first-generation mutant IDH inhibitors and highlight the potential for combination treatment strategies and new metabolic targets.

Isocitrate dehydrogenase gene variants in cancer and their clinical significance

Human isocitrate dehydrogenase (IDH) genes encode for the IDH1, 2 & 3 isoenzymes which catalyse the formation of 2-oxoglutarate from isocitrate and are essential for normal mammalian metabolism. Although mutations in these genes in cancer were long thought to lead to a 'loss of function', combined genomic and metabolomic studies led to the discovery that a common IDH 1 mutation, present in low-grade glioma and acute myeloid leukaemia (AML), yields a variant (R132H) with a striking change of function leading to the production of (2R)-hydroxyglutarate (2HG) which consequently accumulates in large quantities both within and outside cells. Elevated 2HG is proposed to promote tumorigenesis, although the precise mechanism by which it does this remains uncertain. Inhibitors of R132H IDH1, and other subsequently identified cancer-linked 2HG producing IDH variants, are approved for clinical use in the treatment of chemotherapy-resistant AML, though resistance enabled by additional substitutions has emerged. In this review, we provide a current overview of cancer linked IDH mutations focussing on their distribution in different cancer types, the effects of substitution mutations on enzyme activity, the mode of action of recently developed inhibitors, and their relationship with emerging resistance-mediating double mutations.

Chordoma: A Review and Differential Diagnosis

CONTEXT.—

Chordomas are uncommon malignant neoplasms with notochordal differentiation encountered by neuropathologists, bone/soft tissue pathologists, and general surgical pathologists. These lesions most commonly arise in the axial skeleton. Optimal therapy typically involves complete surgical resection, which is often technically difficult owing to the anatomic location, leading to a high rate of recurrence. Lesions have been generally resistant to radiation and chemotherapy; however, experimental studies involving targeted therapy and immunotherapy are currently underway.

OBJECTIVE.—

To summarize the clinical and pathologic findings of the various types of chordoma (conventional chordoma, dedifferentiated chordoma, and poorly differentiated chordoma), the differential diagnosis, and recent advances in molecular pathogenesis and therapeutic modalities that are reliant on accurate diagnosis.

DATA SOURCES.—

Literature review based on PubMed searches containing the term "chordoma" that address novel targeted and immunomodulatory therapeutic modalities; ongoing clinical trials involved in treating chordoma with novel therapeutic modalities identified through the Chordoma Foundation and ClinicalTrials.gov; and the authors' practice experience combined with various authoritative texts concerning the subject.

CONCLUSIONS.—

Chordoma is a clinically and histologically unique malignant neoplasm, and numerous diagnostic considerations must be excluded to establish the correct diagnosis. Treatment options have largely been centered on surgical excision with marginal results; however, novel therapeutic options including targeted therapy and immunotherapy are promising means to improve prognosis.

Prognostic importance of IDH mutations in chondrosarcoma: An individual patient data meta-analysis

Introduction

IDH1/2 mutations are prevalent in cartilaginous tumors including chondrosarcoma. This meta‐analysis using individual patient data (IPD) aimed to investigate the clinical and prognostic association of these mutations in chondrosarcoma patients.

Methods

Two electronic databases including PubMed and Web of Science were searched for relevant data. We included studies providing IPD of chondrosarcoma with available IDH1/2 mutational status for meta‐analysis. Chi‐square and t‐test were performed to compare the groups with and without IDH1/2 mutations. For survival analysis, log‐rank test, and Cox proportional hazards model were used to investigate the association of IDH mutations with patient outcomes.

Results

Fourteen studies with 488 patients were analyzed. IDH1 and IDH2 mutations were detected in 38.7% and 12.1% of cases, respectively. IDH1/2 mutations were significantly associated with an older age (p = 0.003), tumor origins (p < 0.001), tumor grades (p < 0.001), larger diameter (p = 0.003), relapse (p = 0.014), and patient mortality (p = 0.04). Multivariate Cox regression analysis adjusted for age, gender, tumor grade, and tumor sites confirmed the negative impact of IDH1/2 mutations on patient overall survival (HR = 1.90; 95% CI = 1.06–3.42; p = 0.03).

Conclusion

Our meta‐analysis demonstrated the distinct characteristics of IDH1/2‐mutated chondrosarcomas in comparison to those without mutations. These mutations could serve as an independent prognostic biomarker to better prognosticate patient outcomes and design appropriate treatment plans.

Discovery and Optimization of 2H-1λ2-Pyridin-2-one Inhibitors of Mutant Isocitrate Dehydrogenase 1 for the Treatment of Cancer

Neomorphic mutations in isocitrate dehydrogenase 1 (IDH1) are oncogenic for a number of malignancies, primarily low-grade gliomas and acute myeloid leukemia. We report a medicinal chemistry campaign around a 7,7-dimethyl-7,8-dihydro-2H-1λ2-quinoline-2,5(6H)-dione screening hit against the R132H and R132C mutant forms of isocitrate dehydrogenase (IDH1). Systematic SAR efforts produced a series of potent pyrid-2-one mIDH1 inhibitors, including the atropisomer (+)-119 (NCATS-SM5637, NSC 791985). In an engineered mIDH1-U87-xenograft mouse model, after a single oral dose of 30 mg/kg, 16 h post dose, between 16 and 48 h, (+)-119 showed higher tumoral concentrations that corresponded to lower 2-HG concentrations, when compared with the approved drug AG-120 (ivosidenib).

Association of Clinicopathological Features With Outcome in Chondrosarcomas of the Head and Neck

OBJECTIVE

The aim of this study is to assess the association between clinical and radiological features as well as of isocitrate dehydrogenase 1 and 2 (IDH 1,2) mutations with outcome in head and neck chondrosarcomas.

STUDY DESIGN

Retrospective study.

SETTING

Tertiary referral center.

METHODS

Clinical, histological, and molecular data of patients with head and neck chondrosarcomas treated by surgery were collected.

RESULTS

Forty-six patients were included. The mean age at diagnosis was 56 years (range, 17-78). The tumor originated from the skull base (52.2%), facial bones (28.2%), or laryngotracheal area (19.6%). At last follow-up (median 52.5 months), 38 patients were alive, 30 of which were disease free, whereas 8 had died, 4 of disease progression and 4 of other causes. Fourteen (30.4%) had local recurrence and 2 (4.3%) had lung metastasis. All cases were negative for cytokeratin AE1/AE3, brachyury, and IDH1 at immunohistochemistry, while Sanger sequencing identified IDH1/2 point mutations, typically IDH1 R132C, in 9 (37.5%) tumors arising from the skull base. Margin infiltration on the surgical specimen negatively affected the outcome, whereas no correlation was identified with IDH mutation status.

CONCLUSIONS

An adequate margin positively affects survival. IDH mutation status does not affect patient outcome.

Exophytic Lumbar Vertebral Body Mass in an Adult with Back Pain

Chordomas are rare primary bone malignancies derived from notochord remnants. The tumors often are slow-growing and often present with indolent, nonspecific symptoms. Nevertheless, chordomas are locally aggressive and highly prone to local recurrence, necessitating precise planning before biopsy and/or surgical resection. Familiarity with the imaging features of chordomas is, therefore, essential. This case highlights the typical imaging and pathologic features of a spinal chordoma as well as the surgical approach and the patient's subsequent outcome.

Chordomas: A review with emphasis on their pathophysiology, pathology, molecular biology, and genetics

Chordomas are uncommon, bone, axial, or (rarely) extra-axial tumors that are malignant and frequently recur but less commonly metastasize. They usually affect adults, with a very small proportion being pediatric tumors. For children, such tumors present a different biology, since they are more common as scull rather than sacral tumors, with aggressive histological features, including a loss of SMARCB1/INI1 and a dismal prognosis. Histologically, chordomas, believed to derive from notochordal tissue, characteristically show physaliphorous cells in a myxoid or chondroid matrix. Dedifferentiated and poorly differentiated forms can be observed. Moreover, a grading scale for chordomas has been proposed. Cytokeratin, EMA, S100, and brachyury are expressed by most chordomas. These are chemo-resistant tumors, for which surgical resection and/or radiotherapy are the treatments of choice. In this review, the histological, immunohistochemical, molecular, and clinical data of chordomas are discussed.

Central and Peripheral Metabolic Defects Contribute to the Pathogenesis of Alzheimer's Disease: Targeting Mitochondria for Diagnosis and Prevention

Significance: Epidemiological studies indicate that metabolic disorders are associated with an increased risk for Alzheimer's disease (AD). Metabolic remodeling occurs in the central nervous system (CNS) and periphery, even in the early stages of AD. Mitochondrial dysfunction has been widely accepted as a molecular mechanism underlying metabolic disorders. Therefore, focusing on early metabolic changes, especially from the perspective of mitochondria, could be of interest for early AD diagnosis and intervention. Recent Advances: We and others have identified that the levels of several metabolites are fluctuated in the periphery before their accumulation in the CNS, which plays an important role in the pathogenesis of AD. Mitochondrial remodeling is likely one of the earliest signs of AD, linking nutritional imbalance to cognitive deficits. Notably, by improving mitochondrial function, mitochondrial nutrients efficiently rescue cellular metabolic dysfunction in the CNS and periphery in individuals with AD. Critical Issues: Peripheral metabolic disorders should be intensively explored and evaluated for the early diagnosis of AD. The circulating metabolites derived from mitochondrial remodeling represent novel potential diagnostic biomarkers for AD that are more readily detected than CNS-oriented biomarkers. Moreover, mitochondrial nutrients provide a promising approach to preventing and delaying AD progression. Future Directions: Abnormal mitochondrial metabolism in the CNS and periphery is involved in AD pathogenesis. More clinical studies provide evidence for the suitability and reliability of circulating metabolites and cytokines for the early diagnosis of AD. Targeting mitochondria to rewire cellular metabolism is a promising approach to preventing AD and ameliorating AD-related metabolic disorders.

Phase I Study of the Mutant IDH1 Inhibitor Ivosidenib: Safety and Clinical Activity in Patients With Advanced Chondrosarcoma

PURPOSE

Surgery is the primary therapy for localized chondrosarcoma; for locally advanced and/or metastatic disease, no known effective systemic therapy exists. Mutations in the isocitrate dehydrogenase 1/2 (IDH1/2) enzymes occur in up to 65% of chondrosarcomas, resulting in accumulation of the oncometabolite D-2-hydroxyglutarate (2-HG). Ivosidenib (AG-120) is a selective inhibitor of mutant IDH1 approved in the United States for specific cases of acute myeloid leukemia. We report outcomes of patients with advanced chondrosarcoma in an ongoing study exploring ivosidenib treatment.

PATIENTS AND METHODS

This phase I multicenter open-label dose-escalation and expansion study of ivosidenib monotherapy enrolled patients with mutant IDH1 advanced solid tumors, including chondrosarcoma. Ivosidenib was administered orally (100 mg twice daily to 1,200 mg once daily) in continuous 28-day cycles. Responses were assessed every other cycle using RECIST (version 1.1).

RESULTS

Twenty-one patients (escalation, n = 12; expansion, n = 9) with advanced chondrosarcoma received ivosidenib (women, n = 8; median age, 55 years; range, 30-88 years; 11 had received prior systemic therapy). Treatment-emergent adverse events (AEs) were mostly grade 1 or 2. Twelve patients experienced grade ≥ 3 AEs; only one event was judged treatment related (hypophosphatemia, n = 1). Plasma 2-HG levels decreased substantially in all patients (range, 14%-94.2%), to levels seen in healthy individuals. Median progression-free survival (PFS) was 5.6 months (95% CI, 1.9 to 7.4 months); the PFS rate at 6 months was 39.5%. Eleven (52%) of 21 patients experienced stable disease.

CONCLUSION

In patients with chondrosarcoma, ivosidenib showed minimal toxicity, substantial 2-HG reduction, and durable disease control. Future studies of ivosidenib monotherapy or rational combination approaches should be considered in patients with advanced mutant IDH1 chondrosarcoma.

The heterocyclic compound Tempol inhibits the growth of cancer cells by interfering with glutamine metabolism

Tempol (4-hydroxy-2,2,6,6-Tetramethylpiperidine-1-oxyl, TPL), a nitroxide compound, inhibits proliferation and increases the vulnerability of cancer cells to apoptosis induced by cytotoxic agents. However, the molecular mechanism of TPL inhibiting cancer cell proliferation has not been fully understood. In this study, we evaluated the metabolic effect of TPL on cancer cells and explored its cancer therapeutic potential. Extracellular flow assays showed that TPL inhibited cellular basal and maximal oxygen consumption rates of mitochondrial. ¹³C metabolic flux analysis showed that TPL treatment had minimal effect on glycolysis. However, we found that TPL inhibits glutamine metabolism by interfering with the oxidative tricarboxylic acid cycle (TCA) process and reductive glutamine process. We found that the inhibitory effect of TPL on metabolism occurs mainly on the step from citrate to α-ketoglutarate or vice versa. We also found that activity of isocitrate dehydrogenase IDH1 and IDH2, the key enzymes in TCA, were inhibited by TPL treatment. In xenograft mouse model, TPL treatment reduced tumor growth by inhibiting cellular proliferation of xenograft tumors. Thus, we provided a mechanism of TPL inhibiting cancer cell proliferation by interfering with glutamine utilization that is important for survival and proliferation of cancer cells. The study may help the development of a therapeutic strategy of TPL combined with other anticancer medicines.

Distinct clinical and prognostic implication of IDH1/2 mutation and other most frequent mutations in large duct and small duct subtypes of intrahepatic cholangiocarcinoma

Background

Isocitrate dehydrogenase 1/2 (IDH1/2), BAP1, ARID1A and PBRM1 have been reported as the most frequent mutant genes in intrahepatic cholangiocarcinoma (ICC), and their relationships with clinicopathological features and prognosis were researched in this study.

Methods

We collected clinical data of 130 ICC patients from January 2012 to December 2017. The IDH1/2 mutation and loss of BAP1, ARID1A and PBRM1 expressions were detected by DNA sequencing or immunohistochemical methods, and histological subtype of ICCs was determined by hematoxylin-eosin, Alcian blue and S100P staining.

Results

IDH1/2 mutation was related to decreased preoperative serum total bilirubin (P = 0.039), ferritin (P = 0.000) and higher histological differentiation (P = 0.024), and was associated with prolonged disease-free survival (P = 0.009) and a trend toward increased overall survival (P = 0.126) in small duct type of ICCs. Immunohistochemical staining results of MsMab-1 were generally consistent with DNA sequencing for IDH1/2 mutant in ICCs (κ = 0.691). Only BAP1 expression loss was correlated to prolonged disease-free survival (P = 0.031) and overall survival (P = 0.041) in large duct type of ICCs.

Conclusions

IDH1/2 mutation is a favorable predictor and may be related to iron metabolism in small duct type of ICCs. Furthermore, we suggest that the detection of IDH1/2 mutation is indispensable to determine targeted therapy in small duct type ICCs, while it is not necessary in large duct of ICCs. MsMab-1 is a relatively effective multi-specific antibody against IDH1/2 mutant in ICCs. BAP1 expression loss was correlated with improved prognosis only in large duct type ICCs.

Intracranial Mesenchymal Chondrosarcoma Lacking the Typical Histopathological Features Diagnosed by HEY1-NCOA2 Gene Fusion

Intracranial mesenchymal chondrosarcoma (MCS) is a rare neoplasm. The diagnosis of MCS is confirmed by the presence of a biphasic pattern on histological examination, comprising undifferentiated small round cells admixed with islands of well-differentiated hyaline cartilage; however, a differential diagnosis may be challenging in some cases. A 28-year-old woman with a 2-month history of headache was referred to our hospital. Radiologic studies showed an extra-axial lobulated mass composed of calcified and uncalcified areas occupying the left middle fossa. Surgical resection was planned, but her headache suddenly worsened before her planned hospital admission and she was admitted as an emergency. Radiologic studies showed an acute hemorrhage in the uncalcified part of the mass. The mass was resected via the left zygomatic approach after embolization of the feeder vessels. The most likely histopathological diagnosis was MCS. However, the typical bimorphic pattern was not identified in our surgical samples; each undifferentiated area and well-differentiated area was observed separately in different tissue specimens, and no islands of well-differentiated hyaline cartilage were identified within the undifferentiated areas in the same specimen. Molecular assays confirmed the presence of HEY1-NCOA2 fusion. IRF2BP2-CDX1 fusion and IDH1/2 mutations were negative. The final diagnosis of MCS was made based on the presence of HEY1-NCOA2 gene fusion. MCS should be included in the differential diagnosis when radiologic studies show an extra-axial lobulated mass with calcification. Furthermore, molecular demonstration of HEY1-NCOA2 gene fusion may help make a precise diagnosis of MCS, especially in surgical samples lacking the typical histopathological features.

Soft Tissue Special Issue: Chondroid Neoplasms of the Skull

Clinically, radiologically, and pathologically, chondroid neoplasms of the skull can be diagnostically challenging due to overlapping features in each of these domains. Compounding the problem for the pathologist, there is also significant morphologic, immunophenotypic, and molecular genetic overlap between benign and malignant cartilaginous lesions, and the majority of these lesions are encountered quite rarely in routine surgical pathology practice. Each of these factors contribute to the diagnostic difficulty posed by these lesions, highlighting the importance of radiologic-pathologic correlation in the diagnosis. This review is intended to provide an update for surgical pathologists on some of the most commonly encountered chondroid neoplasms in the skull, and includes the following lesions: chondromyxoid fibroma, synovial chondromatosis, chondrosarcoma and variants, and chordoma and variants. For each of these lesions, the differential diagnosis and useful ancillary tests will be discussed in the context of a broad range of additional primary and secondary lesions.

Emerging drug profile: Krebs cycle and cancer: IDH mutations and therapeutic implications

Mutations in IDH1 and IDH2 genes occur frequently in myeloid malignancies and certain solid tumors. IDH1 and IDH2 are enzymes that are involved in the tricarboxylic acid (TCA) cycle. Activating mutations in IDH1 and IDH2 leads to increased production of 2-hydroxygluterate and epigenetic modification, affecting cell differentiation. Small molecule inhibitors of mutated IDH1 and IDH2 have shown promising anti-cancer activity in both preclinical models and early clinical trials. Recently, enasidenib and ivosidenib, oral inhibitors of mutated IDH2 and IDH1 genes, respectively, were approved for use in relapsed or refractory acute myeloid leukemia. This review will focus on the underlying biological mechanism and clinical relevance of IDH mutations in cancer.

Updates in Primary Bone Tumors: Current Challenges and New Opportunities in Cytopathology

The review summarizes the current diagnostic challenges in fine-needle aspiration of primary bone tumors, with focus on the application of new molecular and immunohistochemical techniques in the diagnosis of giant cell-rich neoplasms, chondrosarcomas, and notochordal tumors.

Sellar chondrosarcoma presenting with amenorrhea: A case report

RATIONALE

Intracranial chondrosarcomas are rare entities and most of which arise off the midline. Chondrosarcomas that occur in the sellar region are extremely rare, and to the best of our knowledge, there is no reporting about sellar chondrosarcoma with amenorrhea as the onset symptom.

PATIENT CONCERNS

A 45-year-old woman presented with a 7-month history of amenorrhea and a 3-month history of progressive visual loss in the left eye.

DIAGNOSIS

The patient was diagnosed with recurrent sellar chondrosarcoma arising from intrasellar with extensive tumor invasion into bilateral sphenoid sinuses.

INTERVENTIONS

Twice endonasal transsphenoidal tumorectomies were performed followed with a stereotactic radiotherapy and hormone replacement therapy.

OUTCOMES

The patient's condition was stable and her visual symptoms improved, the hormones returned to normal, and no recurrence was noted on MRI after six months.

LESSONS

Sellar chondrosarcomas with the onset of endocrine dysfunctions are extremely rare, which may be misdiagnosed as pituitary adenoma and the definitive diagnosis depends on histopathological and immunohistochemical evidence. The first choice of treatment is surgery with the goal of complete resection, and postoperative adjuvant radiotherapy should be highlighted.

IDH1 mutation correlates with a beneficial prognosis and suppresses tumor growth in IHCC

BACKGROUND

Isocitrate dehydrogenase 1/2 (IDH1/2) mutations have been reported in intrahepatic cholangiocarcinoma (IHCC). However, the prognosis of a single IDH1 mutation and impact of mutant IDH1 on IHCC tumor growth remain unclear.

METHODS

A total of 85 IHCC tumor samples were sequenced. Prognosis and clinicopathological correlation were analyzed. The role of mutant IDH1 in IHCC tumor growth was measured by cell proliferation assay, colony formation assay in soft agar, and xenograft tumor models. Akt, ERK, p38 MAPK, and JNK signaling, which commonly affect tumor growth, were examined by Western blotting to explore the potential mechanism.

RESULTS

IDH1 mutations correlated with a beneficial prognosis and smaller tumor size. Mutant IDH1 exhibited a growth-inhibitory effect on IHCC cell lines in vitro and in vivo. Akt signaling was suppressed in IHCC cell lines expressing a mutant IDH1. The reactivation of Akt signaling by SC79 restored the inhibited growth of cell lines expressing a mutant IDH1 in IHCC.

CONCLUSIONS

Collectively, we demonstrated that mutant IDH1 correlates with a beneficial prognosis and inhibits tumor growth by suppressing Akt signaling in IHCC. We suggest that patients with IDH1 mutations could be considered for both less-aggressive therapy and therapy tailored to the presence of their mutant enzyme in the future.

The role of metabolic enzymes in mesenchymal tumors and tumor syndromes: genetics, pathology, and molecular mechanisms

The discovery of mutations in genes encoding the metabolic enzymes isocitrate dehydrogenase (IDH), succinate dehydrogenase (SDH), and fumarate hydratase (FH) has expanded our understanding not only of altered metabolic pathways but also epigenetic dysregulation in cancer. IDH1/2 mutations occur in enchondromas and chondrosarcomas in patients with the non-hereditary enchondromatosis syndromes Ollier disease and Maffucci syndrome and in sporadic tumors. IDH1/2 mutations result in excess production of the oncometabolite (D)-2-hydroxyglutarate. In contrast, SDH and FH act as tumor suppressors and genomic inactivation results in succinate and fumarate accumulation, respectively. SDH deficiency may result from germline SDHA, SDHB, SDHC, or SDHD mutations and is found in autosomal-dominant familial paraganglioma/pheochromocytoma and Carney-Stratakis syndrome, describing the combination of paraganglioma and gastrointestinal stromal tumor (GIST). In contrast, patients with the non-hereditary Carney triad, including paraganglioma, GIST, and pulmonary chondroma, usually lack germline SDH mutations and instead show epigenetic SDH complex inactivation through SDHC promoter methylation. Inactivating FH germline mutations are found in patients with hereditary leiomyomatosis and renal cell cancer (HLRCC) syndrome comprising benign cutaneous/uterine leiomyomas and renal cell carcinoma. Mutant IDH, SDH, and FH share common inhibition of α-ketoglutarate-dependent oxygenases such as the TET family of 5-methylcytosine hydroxylases preventing DNA demethylation, and Jumonji domain histone demethylases increasing histone methylation, which together inhibit cell differentiation. Ongoing studies aim to better characterize these complex alterations in cancer, the different clinical phenotypes, and variable penetrance of inherited and sporadic cancer predisposition syndromes. A better understanding of the roles of metabolic enzymes in cancer may foster the development of therapies that specifically target functional alterations in tumor cells in the future. Here, the physiologic functions of these metabolic enzymes, the mutational spectrum, and associated functional alterations will be discussed, with a focus on mesenchymal tumor predisposition syndromes.

IDH1/2 Mutations Predict Shorter Survival in Chondrosarcoma

Background. Recent studies have shown that isocitrate dehydrogenase 1/2 (IDH1/2)- activating mutations occur in a variety of cancers, including acute myeloid leukaemia, gliomas, and chondrosarcomas (CHS)s. The effect of IDH1/2 mutation on overall survival (OS) has not been reported in CHS. The aim of our study was to assess the prevalence of known cancer-related gene mutations in CHS, as well as their prognostic role in patient survival.

Methods. DNA from FFPE samples of 80 patients (F:M- 1:1.3; mean age: 58 years; range 27-86) with histologically confirmed CHS (G1:29; G2:34; G3:17) was subjected to library preparation with the Ion AmpliSeq Cancer Hotspot Panel v2 and sequenced on the PGM Ion Torrent.

Results. Among the clinical features only histological grade influenced OS. Deep sequencing identified 1784 single nucleotide variants. Of them, 426 were considered to be pathogenic or probably pathogenic. Activating IDH1/2 mutations were found in 27 patients (34%) including 17 R132 IDH1 (21%), 10 R172 IDH2 (13%) and 3 R140 IDH2 variants (4%). Three patients had concurrent IDH1 and IDH2 mutations. The R140 IDH2 mutant has not been reported to date in CHS patients. OS for CHS patients with IDH1/2 mutations was significantly lower than in patients without mutations (93% vs 64%; p<0.001). No other genetic feature of the Cancer Hotspot Panel had an impact on OS.

Conclusions. In CHS, IDH1/2-mutation status and the histological aggressiveness of the CHS are important predictors for OS. The R140 IDH2 may also be a novel target for the treatment of CHS patients.

BRAF V600E, TERT promoter mutations and CDKN2A/B homozygous deletions are frequent in epithelioid glioblastomas: a histological and molecular analysis focusing on intratumoral heterogeneity

Epithelioid glioblastoma (E-GBM) is a rare aggressive variant of IDH-wildtype glioblastoma newly recognized in the 2016 World Health Organization classification, composed predominantly of monotonous, patternless sheets of round cells with laterally positioned nuclei and plump eosinophilic cytoplasm. Approximately 50% of E-GBM harbor BRAF V600E, which is much less frequently found in other types of glioblastomas. Most E-GBM are recognized as primary/de novo lesions; however, several E-GBM with co- or pre-existing lower-grade lesions have been reported. To better understand associations between E-GBM and the lower-grade lesions, we undertook a histological and molecular analysis of 14 E-GBM, 10 of which exhibited lower-grade glioma-like components (8 E-GBM with co-existing diffuse glioma-like components, 1 E-GBM with a co-existing PXA-like component and 1 E-GBM with a pre-existing PXA). Molecular results demonstrated that the prevalence of BRAF V600E, TERT promoter mutations and CDKN2A/B homozygous deletions in E-GBM were 13/14 (93%), 10/14 (71%) and 11/14 (79%), respectively, and concurrent BRAF V600E, TERT promoter mutations and CDKN2A/B homozygous deletions were observed in 7/14 (50%) of E-GBM. These alterations were also frequently seen in the lower-grade lesions irrespective of the histology. Genetic analysis including array comparative genomic hybridization performed for 5 E-GBM with co- and pre-existing lower-grade components revealed that all molecular changes found in the lower-grade components were also observed in the E-GBM components, and additional changes were detected in the E-GBM components. In conclusion, E-GBM frequently exhibit BRAF V600E, TERT promoter mutations and CDKN2A/B homozygous deletions and these alterations tend to coexist in E-GBM. Taken together with the facts that only one PXA preceded E-GBM among these lower-grade lesions, and that co-occurrence of BRAF V600E, TERT promoter mutations and CDKN2A/B homozygous deletions have been reported to be rare in conventional lower-grade diffuse gliomas, the diffuse glioma-like components may be distinct infiltrative components of E-GBM, reflecting intratumoral heterogeneity.

Advances in sarcoma gene mutations and therapeutic targets

Sarcomas are rare and complex malignancies that have been associated with a poor prognostic outcome. Over the last few decades, traditional treatment with surgery and/or chemotherapy has not significantly improved outcomes for most types of sarcomas. In recent years, there have been significant advances in the understanding of specific gene mutations that are important in driving the pathogenesis and progression of sarcomas. Identification of these new gene mutations, using next-generation sequencing and advanced molecular techniques, has revealed a range of potential therapeutic targets. This, in turn, may lead to the development of novel agents targeted to different sarcoma subtypes. In this review, we highlight the advances made in identifying sarcoma gene mutations, including those of p53, RB, PI3K and IDH genes, as well as novel therapeutic strategies aimed at utilizing these mutant genes. In addition, we discuss a number of preclinical studies and ongoing early clinical trials in sarcoma targeting therapies, as well as gene editing technology, which may provide a better choice for sarcoma patient management.

Chordoma of the Head and Neck: A Review

Chordoma is a rare malignant bone tumor that can arise anywhere along the central neural axis and many involve head and neck sites, most commonly the skull base. The relative rarity of these tumors, combined with the complex anatomy of the head and neck, pose diagnostic challenges to pathologists. This article describes the pertinent clinical, pathologic, and molecular features of chordomas and describes how these features can be used to aid in formulating a differential diagnosis. Emphasis is placed on key diagnostic pitfalls and the importance of incorporating immunohistochemical information into the diagnosis.

Integrating Morphology and Genetics in the Diagnosis of Cartilage Tumors

Cartilage-forming tumors of bone are a heterogeneous group of tumors with different molecular mechanisms involved. Enchondromas are benign hyaline cartilage-forming tumors of medullary bone caused by mutations in IDH1 or IDH2. Osteochondromas are benign cartilage-capped bony projections at the surface of bone. IDH mutations are also found in dedifferentiated and periosteal chondrosarcoma. A recurrent HEY1-NCOA2 fusion characterizes mesenchymal chondrosarcoma. Molecular changes are increasingly used to improve diagnostic accuracy in chondrosarcomas. Detection of IDH mutations or HEY1-NCOA2 fusions has already proved their immense value, especially on small biopsy specimens or in case of unusual presentation.

Radiation-induced gliomas: a report of four cases and analysis of molecular biomarkers

Radiation-induced glioma (RIG) is a rare secondary glioma. The tumors morphologically resemble their sporadically arising counterparts. Recently, the WHO classification of tumors of the central nervous system was revised to incorporate molecular biomarkers together with classic histological features. The status of molecular biomarkers in RIG, however, remains unclear. The objective of this study was to investigate if commonly accepted glioma-specific biomarkers are relevant in RIGs. Among 269 gliomas diagnosed as WHO grade 2, 3 and 4 in our institution, four were diagnosed as RIGs. Immunohistochemical (IHC) staining for isocitrate dehydrogenase 1 (IDH1), p53, alpha thalassemia/mental retardation syndrome X-linked (ATRX), and H3K27M, and direct DNA sequencing of IDH1/2, telomerase reverse transcriptase (TERT) promoter, Histone H3.3 (H3F3A) and B-Raf (BRAF) genes was performed. All tumor specimens were IDH1-, p53- and H3K27M-negative. The nuclei of tumor cells in all cases exhibited positive staining for ATRX. In direct DNA sequencing analysis, no IDH1, IDH2, TERT promoter, H3F3A or BRAF mutations were found in any of the cases. Our findings suggest that these characteristic glioma-associated molecular mutations may be rare events in RIGs. More RIGs need to be tested for analysis of molecular biomarkers to clarify the clinical and histopathological spectra of this tumor.

Molecular Pathogenesis and Diagnostic, Prognostic and Predictive Molecular Markers in Sarcoma

Sarcomas are infrequent mesenchymal neoplasms characterized by notable morphological and molecular heterogeneity. Molecular studies in sarcoma provide refinements to morphologic classification, and contribute diagnostic information (frequently), prognostic stratification (rarely) and predict therapeutic response (occasionally). Herein, we summarize the major molecular mechanisms underlying sarcoma pathogenesis and present clinically useful diagnostic, prognostic and predictive molecular markers for sarcoma. Five major molecular alterations are discussed, illustrated with representative sarcoma types, including 1. the presence of chimeric transcription factors, in vascular tumors; 2. abnormal kinase signaling, in gastrointestinal stromal tumor; 3. epigenetic deregulation, in chondrosarcoma, chondroblastoma, and other tumors; 4. deregulated cell survival and proliferation, due to focal copy number alterations, in dedifferentiated liposarcoma; 5. extreme genomic instability, in conventional osteosarcoma as a representative example of sarcomas with highly complex karyotype.

Isocitrate dehydrogenases in physiology and cancer: biochemical and molecular insight

Isocitrate dehydrogenases play important roles in cellular metabolism and cancer. This review will discuss how the roles of isoforms 1 and 2 in normal cell and cancer metabolism are distinct from those of isoform 3. It will also explain why, unlike 1 and 2, mutations in isoform 3 in tumor are not likely to be driver ones. A model explaining two important features of isocitrate dehydrogenases 1 and 2 mutations, their dominant negative effect and their mutual exclusivity, will be provided. The importance of targeting these mutations and the possibility of augmenting such therapy by targeting other cancer-related pathways will also be discussed.

Genetic aberrations and molecular biology of skull base chordoma and chondrosarcoma

Chordomas and chondrosarcomas are two major malignant bone neoplasms located at the skull base. These tumors are rarely metastatic, but can be locally invasive and resistant to conventional chemotherapies and radiotherapies. Accordingly, therapeutic approaches for the treatment of these tumors can be difficult. Additionally, their location at the skull base makes them problematic. Although accurate diagnosis of these tumors is important because of their distinct prognoses, distinguishing between these tumor types is difficult due to overlapping radiological and histopathological findings. However, recent accumulation of molecular and genetic studies, including extracranial location analysis, has provided us clues for accurate diagnosis. In this report, we review the genetic aberrations and molecular biology of these two tumor types. Among the abundant genetic features of these tumors, brachyury immunohistochemistry and direct sequencing of IDH1/2 are simple and useful techniques that can be used to distinguish between these tumors. Although it is still unclear why these tumors, which have such distinct genetic backgrounds, show similar histopathological findings, comparison of their genetic backgrounds could provide essential information.

Distinctive Head and Neck Bone and Soft Tissue Neoplasms

Benign and malignant primary bone and soft tissue lesions of the head and neck are rare. The uncommon nature of these tumors, combined with the complex anatomy of the head and neck, pose diagnostic challenges to pathologists. This article describes the pertinent clinical, radiographic, and pathologic features of selected bone and soft tissue tumors involving the head and neck region, including angiofibroma, glomangiopericytoma, rhabdomyosarcoma, biphenotypic sinonasal sarcoma, chordoma, chondrosarcoma, and osteosarcoma. Emphasis is placed on key diagnostic pitfalls, differential diagnosis, and the importance of correlating clinical and radiographic information, particularly for tumors involving bone.

Chondroma arising from the spinal dura mater at the thoracic level: A case report with molecular analysis

Chondromas are benign tumors that can be found at several sites in the body, while those arising from the dura mater are extremely rare. Among them, although chondromas arising from the cranial dura mater have been reported, those arising from the spinal dura mater have not been reported in the literature to date. A 66-year-old woman presented with right-sided continuous backache which she had developed recently. After detailed examinations, an epidural tumor at the thoracic level was detected. The patient underwent surgery and a total en-bloc resection was accomplished. From the clinical and pathological findings, the tumor was revealed as chondroma arising from the spinal dura mater. A recent comprehensive study has identified the isocitrate dehydrogenase 1 (IDH1) and IDH2 mutations in conventional central and periosteal cartilaginous tumors, and it has subsequently been analyzed in intracranial chondrosarcoma and chondroma, including chondroma of the convexity dura mater. Herein, we describe a novel case of chondroma arising from the spinal dura mater, with mutation analysis of IDH1 and IDH2 both of which revealed wild-type.

Quantitative Imaging of D-2-Hydroxyglutarate in Selected Histological Tissue Areas by a Novel Bioluminescence Technique

Patients with malignant gliomas have a poor prognosis with average survival of less than 1 year. Whereas in other tumor entities the characteristics of tumor metabolism are successfully used for therapeutic approaches, such developments are very rare in brain tumors, notably in gliomas. One metabolic feature characteristic of gliomas, in particular diffuse astrocytomas and oligodendroglial tumors, is the variable content of D-2-hydroxyglutarate (D2HG), a metabolite that was discovered first in this tumor entity. D2HG is generated in large amounts due to various “gain-of-function” mutations in the isocitrate dehydrogenases IDH1 and IDH2. Meanwhile, D2HG has been detected in several other tumor entities, including intrahepatic bile-duct cancer, chondrosarcoma, acute myeloid leukemia, and angioimmunoblastic T-cell lymphoma. D2HG is barely detectable in healthy tissue (<0.1 mM), but its concentration increases up to 35 mM in malignant tumor tissues. Consequently, the “oncometabolite” D2HG has gained increasing interest in the field of tumor metabolism. To facilitate its quantitative measurement without loss of spatial resolution at a microscopical level, we have developed a novel bioluminescence assay for determining D2HG in sections of snap-frozen tissue. The assay was verified independently by photometric tests and liquid chromatography/mass spectrometry. The novel technique allows the microscopically resolved determination of D2HG in a concentration range of 0–10 μmol/g tissue (wet weight). In combination with the already established bioluminescence imaging techniques for ATP, glucose, pyruvate, and lactate, the novel D2HG assay enables a comparative characterization of the metabolic profile of individual tumors in a further dimension.

Primary Bone Tumors of the Skull: Spectrum of 125 Cases, with Review of Literature

AIMS

Primary skull bone tumors, benign or malignant, are rare, and include a vast repertoire of lesions. These tumors are not reported systematically in the literature, with most studies being on individual entities or as single case reports.

METHODS

Primary bone tumors diagnosed over a period of 12 years were retrieved, histological diagnoses reviewed, and clinical parameters noted.

RESULTS

We identified 125 primary skull bone tumors. The mean age at diagnosis was 32 years (range: 2-65 years). Majority of patients were adults (82.4%); male preponderance was noted (72.8%). Malignant tumors were more frequent than benign tumors. Most common malignant tumor was chordoma (n = 37), while most common benign tumor was osteoma (n = 7). Tumors were most frequently located at the skull base, of which clivus was most common location. Chordomas accounted for majority of clival tumors, while chondrosarcoma predominated at other skull base locations. Benign tumors were extremely rare in skull base. Tumors of the vault bones were infrequent; with chondrosarcoma and osteoma being the most common malignant and benign tumors, respectively.

CONCLUSIONS

This is the largest series of primary skull bone tumors from India. Documentation of such a series will aid in approaching differential diagnosis of skull tumors in a systematic manner.

Clinical Applications of Molecular Markers in Bone Tumors

Pathologic diagnosis of primary bone neoplasms can be challenging primarily due to rarity of the disease entities, overlapping imaging and histologic findings, and lack of tumor-specific immunohistochemical stains. Although slow to evolve, in recent years there has been a rapid advance in the discovery of new and novel molecular markers in primary bone neoplasms, which has enhanced diagnostic accuracy and has shed light into their pathogenesis. Modern technological approaches such as next-generation sequencing including RNA sequencing are serving as "rapid discovery platforms" for new and novel mutations and translocations with diagnostic, prognostic, and possible therapeutic applicability. As next-generation sequencing technologies are finding their place in clinical laboratories, one could envision routine testing for mutations spanning across a gene or translocations with multiple breakpoints and partner genes. This review will focus on the clinical relevance and applicability of molecular markers in primary bone neoplasms with examples.

Detection of Dual IDH1 and IDH2 Mutations by Targeted Next-Generation Sequencing in Acute Myeloid Leukemia and Myelodysplastic Syndromes

Studies in myeloid neoplasms have described recurrent IDH1 and IDH2 mutations as primarily mutually exclusive. Over a 6-month period of clinical testing with a targeted next-generation sequencing assay, we evaluated 92 patients with acute myeloid leukemia, myelodysplastic syndrome, and chronic myelomonocytic leukemia and identified a subset of 21 patients (23%) who harbored mutations in either IDH1 or IDH2. Of the 21 patients with IDH mutations, 4 (19%) were found to have single nucleotide variants in both IDH1 and IDH2. An additional patient included in the study was found to have two different IDH2 mutations. The mutations were typically present at different variant allelic frequencies, with one predominating over the other, consistent with the presence of multiple subclones in a single patient. In one case, the variant allelic frequencies in both IDH1 and IDH2 were equally low in the setting of a high percentage of blasts, suggesting that the IDH mutations were unlikely to be present in the founding clone. Given these data, we conclude that dual IDH1/2 mutations likely were previously underestimated, a finding that may carry important treatment implications.

TET proteins in cancer: Current 'state of the art'

Aberrations in DNA methylation patterns are observed from the early stages of carcinogenesis. However, the mechanisms that drive these changes remain elusive. The recent characterization of ten-eleven translocation (TET) enzymes as a source of newly modified cytosines (5-hydroxymethylcytosine, 5-formylcytosine and 5-carboxylcytosine) has shed new light on the DNA demethylation process. These cytosines are intermediates of an active DNA demethylation process and are epigenetic markers per se. In this review, we discuss the mechanism and function of TET proteins in biological processes as well as current knowledge regarding their expression and regulation in cancer.