Allelic losses in oligodendroglial and oligodendroglioma-like neoplasms: analysis using microsatellite repeats and polymerase chain reaction

A custom next-generation sequencing panel for 1p/19q codeletion and mutational analysis in gliomas

The World Health Organization has updated their classification system for the diagnosis of gliomas, combining histological features with molecular data including isocitrate dehydrogenase 1 and codeletion of chromosomal arms 1p and 19q. 1p/19q codeletion analysis is commonly performed by fluorescence in situ hybridization (FISH). In this study, we developed a 57-gene targeted next-generation sequencing (NGS) panel including 1p/19q codeletion detection mainly to assess diagnosis and potential treatment response in melanoma, gastrointestinal stromal tumor, and glioma patients. Loss of heterozygosity analysis was performed using the NGS method on 37 formalin-fixed paraffin-embedded glioma tissues that showed 1p and/or 19q loss determined by FISH. Conventional methods were applied for the validation of some glioma-related gene mutations. In 81.1% (30 of 37) and 94.6% (35 of 37) of cases, 1p and 19q were found to be in agreement whereas concordance for 1p/19q codeletion and no 1p/19q codeletion was found in 94.7% (18 of 19) and 94.4% (17 of 18) of cases, respectively. Overall, comparing NGS results with those of conventional methods showed high concordance. In conclusion, the NGS panel allows reliable analysis of 1p/19q codeletion and mutation at the same time.

Treatment Outcomes in 1p19q Co-deleted/Partially Deleted Gliomas

BACKGROUND

Radiotherapy with procarbazine, lomustine, and vincristine improves overall survival (OS) in patients with 1p19q co-deleted anaplastic oligodendroglioma/anaplastic oligoastrocytoma.

METHODS

This retrospective analysis investigated outcomes in patients with 1p19q co-deleted/partially deleted oligodendroglioma, oligoastrocytoma, anaplastic oligodendroglioma, or anaplastic oligoastrocytoma. OS and progression-free survival (PFS) were analyzed using the Kaplan-Meier method and prognostic factors using the Cox proportional hazard model.

RESULTS

A total of 106 patients (between December 1997 and December 2013) were included. Median age was 40 years (19-66), 58 were male (55%), Eastern Cooperative Oncology Group performance status was 0 in 80 patients (75%). 1p19q status was co-deleted in 66 (62%), incompletely co-deleted in 27 (25%), and 1p or 19q loss alone in four (4%) and nine (8%) patients, respectively. Isocitrate dehydrogenase-1 R132H mutation was found in 67 of 85 patients with sufficient material. Upfront treatment was given in 72 (68%) patients and temozolomide alone in 52 (49%). Median time to radiotherapy in 47 patients (44%) was 34.7 months and 41.2 months in 9 patients with co-deleted/incompletely co-deleted anaplastic oligodendroglioma/anaplastic oligoastrocytoma who received upfront temozolomide alone. Median OS was not reached and 5-year OS was 91% for all groups (median follow-up, 5.1 years). On multivariable analysis for all patients, receipt of therapy upfront versus none (p=0.04), PS 1 versus 0 (p<0.001) and 1p19q co-deletion/incomplete deletion versus 1p or 19q loss alone (p=0.005) were prognostic for PFS. Isocitrate dehydrogenase-1 status was not prognostic for PFS.

CONCLUSIONS

With similar survival patterns in low-grade/anaplastic gliomas, molecular characteristics may be more important than histological grade. Longer follow-up and results of prospective trials are needed for definitive guidance on treatment of these patients.

Mass spectrometry-based assay for the molecular diagnosis of glioma: concomitant detection of chromosome 1p/19q codeletion, and IDH1, IDH2, and TERT mutation status

The World Health Organization recently revised the diagnosis of glioma, to integrate molecular parameters, including IDH mutations and codeletion (loss of heterozygosity; LOH) of chromosome arms 1p/19q, into the definitions of adult glioma histological subtypes. Mutations in the TERT promoter may also be useful for glioma diagnosis and prognosis. The integration of molecular markers into routine diagnosis requires their rapid and reliable assessment. We propose a MassARRAY (MS)-based test that can identify 1p/19q codeletion using quantitative SNP genotyping and, simultaneously, characterize hotspot mutations in the IDH1, IDH2, and TERT genes in tumor DNA. We determined the reliability of the MS approach testing 50 gliomas and comparing the MS results with those obtained by standard methods, such as short tandem repeat genotyping, array comparative genomic hybridization (array-CGH) and Fluorescence In Situ Hybridization (FISH) for 1p/19q codeletion and Sanger sequencing for hotspots mutations. The results indicate that MS is suitable for the accurate, rapid, and cost-effective evaluation of chromosome deletions combined with hotspot mutation detection. This MS approach could be similarly exploited in evaluation of LOH in other situations of clinical and/or research importance.

Prognostic value of preoperative von Willebrand factor plasma levels in patients with Glioblastoma

Circulating biomarker for malignant gliomas could improve both differential diagnosis and clinical management of brain tumor patients. Among all gliomas, glioblastoma (GBM) is considered the most hypervascularized tumor with activation of multiple proangiogenic signaling pathways that enhance tumor growth. To investigate whether preoperative antigen plasma level of von Willebrand Factor (VWF:Ag) might be possible marker for GBM onset, progression, and prognosis, we retrospectively examined 57 patients with histological diagnosis for GBM and 23 meningiomas (MNGs), benign intracranial expansive lesions, enrolled as controls. Blood samples were collected from all the patients before tumor resection. Plasma von Willebrand Factor (VWF):Ag levels were determined by using a latex particle‐enhanced immunoturbidimetric assay. The median levels of vWF:Ag were significantly higher in GBMs than in meningiomas (MNGs) (183 vs. 133 IU/dL, P = 0.01). The cumulative 1‐year survival was significantly shorter in patients with VWF:Ag levels >200 IU/dL than in those with levels <200 IU/dL and increased VWF levels were associated with a threefold higher risk of death in GBM patients. Our data suggest that VWF:Ag could be a circulating biomarker of disease malignancy, that could be considered, in association with other genetic and epigenetic factors, currently available in the GBM management. Future studies should investigate whether plasma VWF:Ag levels could also be used to monitor therapeutic effects and whether it may have a prognostic value.

Chromogenic in situ hybridization is a reliable alternative to fluorescence in situ hybridization for diagnostic testing of 1p and 19q loss in paraffin-embedded gliomas

Recent studies imply the importance of rapid and reliable diagnostic assessment of 1p/19q status in oligodendroglial tumors. To date, fluorescence in situ hybridization (FISH) is the most commonly applied technique. FISH, however, has several technical shortcomings that are suboptimal for diagnostic applications: results must be viewed in a fluorescence microscope, results are usually evaluated by a single investigator only, and signal fading excludes physical archiving. Also, in gliomas, the distinction of diffusely infiltrating tumor cells from reactively altered normal tissue may be challenging in fluorescence microscopy. Dual-color chromogenic in situ hybridization (CISH) has started to replace FISH in some diagnostic tests performed in pathology. Here, we present the first single institute experience with a side-by-side analysis of 1p/19q FISH and CISH in a series of 42 consecutive gliomas. FISH and CISH produced identical results for 1p and 19q in 93% of cases (n = 39/42). Discrepant results were reevaluated by repeated FISH and a polymerase chain reaction (PCR)-based microsatellite marker analysis for loss of heterozygosity. Reevaluation confirmed CISH data in all three cases. We conclude that CISH is a reliable alternative in 1p/19q testing in paraffin-embedded tissues likely to be more sensitive to detect 1p/19q status than FISH analysis.

Long-term epilepsy-associated tumors

The term long-term epilepsy associated tumor (LEAT) encompasses lesions identified in patients investigated for long histories (often 2 years or more) of drug-resistant epilepsy. They are generally slowly growing, low grade, cortically based tumors, more often arising in younger age groups and in many cases exhibit neuronal in addition to glial differentiation. Gangliogliomas and dysembryoplastic neuroepithelial tumors predominate in this group. LEATs are further united by cyto-architectural changes that may be present in the adjacent cortex which have some similarities to developmental focal cortical dysplasias (FCD); these are now grouped as FCD type IIIb in the updated International League Against Epilepsy (ILAE) classification. In the majority of cases, surgical treatments are beneficial from both perspectives of managing the seizures and the tumor. However, in a minority, seizures may recur, tumors may show regrowth or recurrence, and rarely undergo anaplastic progression. Predicting and identifying tumors likely to behave less favorably are key objectives of the neuropathologist. With immunohistochemistry and modern molecular pathology, it is becoming increasingly possible to refine diagnostic groups. Despite this, some LEATs remain difficult to classify, particularly tumors with "non-specific" or diffuse growth patterns. Modification of LEAT classification is inevitable with the goal of unifying terminological criteria applied between centers for accurate clinico-pathological-molecular correlative data to emerge. Finally, establishing the epileptogenic components of LEAT, either within the lesion or perilesional cortex, will elucidate the cellular mechanisms of epileptogenesis, which in turn will guide optimal surgical management of these lesions.

Nogo-A: a useful marker for the diagnosis of oligodendroglioma and for identifying 1p19q codeletion

The differential diagnosis between oligodendrogliomas and other gliomas remains a critical issue. The aim of this study is to verify the diagnostic value of Olig-2, Nogo-A, and synaptophysin and their role in identifying 1p19q codeletion. A total of 168 cases of brain tumors were studied: 24 oligodendrogliomas, 23 anaplastic oligodendrogliomas, 2 oligoastrocytomas, 2 anaplastic oligoastrocytomas, 30 glioblastoma multiforme, 2 diffuse astrocytomas, 4 anaplastic astrocytomas, 10 pilocytic astrocytomas, 9 ependymomas, 12 anaplastic ependymomas, 10 central neurocytomas, 10 meningiomas, 10 choroid plexus papillomas, 10 dysembryoplastic neuroepithelial tumors, and 10 metastases. All cases were immunostained with Olig-2, Nogo-A, and synaptophysin. In 79 cases, the status of 1p/19q had already been assessed by fluorescence in situ hybridization. Thus, in selected cases, fluorescence in situ hybridization was repeated in areas with numerous Nogo-A-positive neoplastic cells. Nogo-A was positive in 18 (75%) of 24 oligodendrogliomas, 8 (80%) of 10 dysembryoplastic neuroepithelial tumors, 6 (20%) of 30 glioblastoma multiforme, and 2 (20%) of 10 pilocytic astrocytomas. Olig-2 stained 22 (91.6%) of 24 oligodendrogliomas and all dysembryoplastic neuroepithelial tumors but also 24 (80%) of 30 glioblastoma multiforme and 8 (80%) of 10 pilocytic astrocytomas. Finally, synaptophysin stained 13 (54.1%) of 24 oligodendrogliomas, 3 (10%) of 30 glioblastoma multiforme, 1 (10%) of 10 pilocytic astrocytomas, and all neurocytomas. Among the 79 tested cases, original fluorescence in situ hybridization showed 1p/19q codeletion in 12 (52.2%) of 23 oligodendrogliomas, 8 (38%) of 21 anaplastic oligodendrogliomas, and 1 (4%) of 25 glioblastoma multiforme. However, after carrying out the Nogo-A-driven fluorescence in situ hybridization, 1p/19q codeletion was observed in 8 additional cases. Nogo-A is more useful and specific than Olig-2 in differentiating oligodendrogliomas from other gliomas. Furthermore, using a Nogo-A-driven fluorescence in situ hybridization analysis, it is possible to identify a larger number of 1p19q codeletions in gliomas.

One hundred and one dysembryoplastic neuroepithelial tumors: an adult epilepsy series with immunohistochemical, molecular genetic, and clinical correlations and a review of the literature

Simple and complex forms of dysembryoplastic neuroepithelial tumors (DNTs) are readily recognizable but forms with diffuse growth pattern, and hybrid tumors, that is, mixed DNT and ganglioglioma (DNT/GG), are more contentious entities. Rare DNTs have shown aggressive behavior. We reviewed cortical growth patterns, immunophenotype (including CD34, nestin and calbindin), genetic profile, and outcome in 101 DNT in adults. Simple (n = 18), complex (n = 31), diffuse (n = 35) DNT, and mixed DNT/GG (n = 17) showed no difference in age of onset, associated seizure type, or outcome (67.5% free from seizure; mean follow-up, 6 years). CD34 was seen in 61%, calbindin in 57%, and nestin in 86% of all DNT types; these markers were less common in simple DNT. Peritumoral cortical changes (Layer I hypercellularity [61%], satellite nodules [51.6%]) were frequent, but dyslamination (cortical dysplasia) was not identified. Molecular genetic abnormalities identified in 17 cases were IDH1 mutation (n = 3), 1p/19q loss (n = 10), isolated loss 9q (n = 2), and PTEN loss (n = 3), which were not associated with tumor type or location, higher cell proliferation, or distinguishing clinical features (mean age of epilepsy onset, 9 years; age at surgery = 31 years; 69% free from seizure); none had progression on magnetic resonance imaging (mean follow-up, 6 years). No single feature was predictive of seizure-free outcome, but there was a trend for better outcome in CD34-positive tumors (p = 0.07). One case has shown transformation to a higher grade. This study supports the existence of a range of subtypes of DNT some with overlapping features with ganglioglioma; molecular genetic abnormalities were not predictive of atypical behavior.

1p19q LOH patterns and expression of p53 and Olig2 in gliomas: relation with histological types and prognosis

In glial tumors, the loss of heterozygosity of the 1p and 19q chromosomal arms is thought to be a marker of good prognosis in oligodendroglial tumors. However, 1p and 19q loss of heterozygosity may be telomeric, interstitial, centromeric or affect the whole arm of the chromosome and the associations between these different patterns and tumor type, other molecular markers and patient prognosis remain unclear. We analyzed microsatellite markers in a region spanning the chromosome from the telomere to the centromere, to characterize the pattern of 1p and 19q loss of heterozygosity in 39 infiltrative gliomas, including astrocytomas, glioblastomas, oligoastrocytomas and oligodendrogliomas. We then studied the association between loss of heterozygosity and the expression of p53 protein and Olig2, as analyzed using immunohistochemistry, and epidermal growth factor receptor (EGFR) gene amplification, as investigated using fluorescence in situ hybridization (FISH). Finally, we assessed the influence of molecular markers on the overall survival of patients. We identified five different 1p19q loss of heterozygosity patterns among the tumors studied and found that loss of heterozygosity over the whole 1p arm was associated with loss of heterozygosity over the whole 19q arm in 90% of cases. 1p19q whole loss was present in all the classical oligodendrogliomas, whereas other 1p19q loss patterns predominated in oligoastrocytomas. 1p19q whole loss was also significantly associated with Olig2 overexpression, but was never observed in tumors overexpressing p53 protein. We also found that, among patients with contrast-enhancing tumors, those with 1p19q whole loss tended to survive for longer. In combination with classical histological and immunohistochemical data, 1p19q status determination provides pertinent information useful for (1) discriminating between histological types of gliomas and (2) identifying a subgroup of tumors that are associated with a better prognosis.

Oligodendroglioma arising in an ovarian mature cystic teratoma

SUMMARY

We describe a case of oligodendroglioma arising in an ovarian mature cystic teratoma associated with a loss of heterozygosity on the long arm of chromosomes 19 and 10. To our knowledge it is the second case reported in the literature at this site and the first one described in association with a characterized genetic alteration. The patient was 29 years old and presented with a history of 4 months of pelvic pain. Ultrasound examination showed a cystic mass arising in the left adnexa suggesting a teratoma. At laparotomy a cystic ovoid mass was found arising from the left adnexa, completely replacing the ovary. An ovariectomy was performed. Macroscopically a multilocular cyst containing hair, sebum, and a relatively well-defined solid zone of grayish-pink color strongly suggestive of a cerebral tissue, was observed. Microscopic analyses confirmed the teratomatous nature of the cyst. The solid area was composed of mature glial tissue in which was observed a proliferation of monotonous cells with round and homogenous nuclei, surrounded by a clear halo of cytoplasm ("honeycomb appearance") which immunohistochemically showed positivity for glial fibrilar acidic protein and for neurofilament protein. Ki-67 labeling index was about 3%. These findings were consistent with a low-grade oligodendroglioma arising in a mature ovarian cystic teratoma. Reverse transcription-polymerase chain reaction analysis showed a characterized loss of heterozygosity occurring in tumor DNA on chromosomes 10q and 19q13.

[Diagnostic and prognostic values of 1p and 19q deletions in adult gliomas: critical review of the literature and implications in daily clinical practice]

Losses of chromosomes 1p and 19q are deemed correlated with diagnosis of oligodendroglioma, higher chemosensitivity and better prognosis. We reviewed the literature to evaluate the usefulness of these correlations in daily clinical practice. The rates of deletions relative to histology (WHO classifications) were extracted from 33 studies, including 2666 patients. The 1p deletions and 1p19q codeletion mean rates were respectively 65.4 and 63.3% in oligodendrogliomas, 28.7 and 21.6% in oligoastrocytomas, 13.2 and 7.5% in astrocytomas, 11.6 and 2.9% in glioblastomas. The presence of 1p deletion and 1p19q codeletion were strongly correlated with the histological diagnosis corresponding to oligodendroglioma. Calculation of specificity, sensitivity, predictive positive values and false negative rates suggests that presence of deletion 1p or codeletion represents a strong argument in favor of the diagnosis of oligodendroglioma. However, considering the high false negative rate, absence of such deletions does not rule out the diagnosis. In grade 3 oligodendroglial tumors, the probability of responding to chemotherapy, and the duration of response, were higher when codeletions were present. This suggests that, in these tumors, the presence of codeletion is a strong argument in favor of adjuvant chemotherapy. However, chemotherapy should not be systematically excluded when codeletions are absent, as the chances of response are about 33% in this situation. Data concerning low-grade gliomas were more controversial. Oligodendroglial tumors with 1p deletion or 1p19q codeletion seemed to have a better prognosis, as five-year survival rates were 50% higher than in tumors without deletion. This might be explained by the correlation between 1p deletion and other identified prognosis factors: (1) higher chemosensitivity, (2) tumor location more frequently in the frontal lobe, leading to better resection and lower risk of neurological deficit, (3) slower growth rate, (4) higher risk of epilepsy, leading to an early detection.

Dysembryoplastic neuroepithelial tumor (DNT)-like oligodendrogliomas or DNTs evolving into oligodendrogliomas: Two illustrative cases

A review of dysembryoplastic neuroepithelial tumors (DNTs) in 14 patients over a 12-year period revealed four patients re-operated because of changes on magnetic resonance imaging (MRI) suggesting tumor recurrence or progression. In three of these, the histological features were identical to the initial DNT. In the fourth patient, persistent DNT was surrounded by WHO grade 2 oligoastrocytoma. In one of the other 10 patients, WHO grade 2 oligodendroglioma was present in white matter deep to and completely separate from a cortically based DNT. Fluorescence in situ hybridization showed codeletion of 1p and 19q in both the DNT and oligodendroglioma and oligoastrocytoma components. Deletions were not identified in any other tumor. Our findings corroborate other studies that 1p and 19q deletions are uncommon in DNT. These two unusual tumors also raise the possibility that rare DNTs may evolve into oligodendroglioma or oligoastrocytoma. DNTs with this altered biology can be identified by 1p and 19q deletion analysis.

Clinicopathologic aspects of 1p/19q loss and the diagnosis of oligodendroglioma

CONTEXT

Significant interobserver variability exists with respect to the diagnosis of oligodendroglial neoplasms, especially their distinction from astrocytoma and mixed oligoastrocytoma. Combined loss of the short arm of chromosome 1 and the long arm of chromosome 19 has been shown to be both relatively specific to oligodendroglioma and, when present, a marker of improved prognosis in patients with these tumors. In addition, 1p/19q loss has been shown to be a marker of "classic" oligodendroglial histology. These findings raise questions as to the role of 1p/19q testing in clinical practice, both as a prognostic marker and as a potential diagnostic marker among infiltrating glial neoplasms.

OBJECTIVE

This review discusses the issues raised above and tries to clarify the current status of 1p/19q evaluation in the diagnosis of oligodendroglioma.

DATA SOURCES

Sources for this review include recent literature as well as the experience of 3 practicing neuropathologists.

CONCLUSIONS

1p/19q status is an important marker in oligodendroglioma. Loss of 1p/19q is associated with classic oligodendroglioma histology as well as improved prognosis. The combined 1p/19q marker will continue to be a clinically useful marker of prognosis and could potentially be incorporated into diagnostic criteria in the future.

Current Strategies in Treatment of Oligodendroglioma: Evolution of Molecular Signatures of Response

Oligodendroglioma frequently (≥ 70%) responds to radiation and chemotherapy, and is the first CNS neoplasm in which a genetic signature (1p and 19q deletion) has been associated with outcome within the context of large clinical trials. Current translational investigations focus on deletions or mutations of potential tumor suppressor genes, epigenetic alterations, amplification or mutation of growth factor and regulatory genes, and characterization of signaling events and regulatory protein expression. The most compelling data has involved 1p and 19q loss, which is observed in over 50% of anaplastic oligodendrogliomas. In two randomized phase III trials (Radiation Therapy Oncology Group 9402 and European Organisation for Research and Treatment of Cancer 26951), the addition of neoadjuvant or adjuvant procarbazine, lomustine, and vincristine (PCV; respectively) to radiotherapy did not produce superior survival as compared with radiotherapy alone. A modest increase in progression-free survival was observed with the addition of PCV, but at the cost of increased toxicity. Combined 1p and 19q loss identified a favorable prognostic group in both studies, which appeared to be independent of treatment arms. However, it is unclear whether these deletions represent surrogate markers of a favorable biologic tumor behavior, or are predictive of outcome after specific treatment. Currently, there is insufficient data to allow therapeutic decisions to be made solely on the basis of 1p and 19q gene deletion status. Future phase III trials are evaluating other chemotherapeutic and targeted agents, including temozolomide, and include correlative investigations of aberrant molecular events in these neoplasms, which may lead to future therapeutic strategies that are based on specific molecular signatures.

Oligodendroglioma: clinical study and survival analysis correlated with chromosomal anomalies

Object

Demonstration of the loss of chromosomes 1p and 19q in the presence of a brain neoplasm marks the emergence of genotype as a prognostic indicator. The authors report gene expression data for oligodendroglioma and correlate genotype with response to therapy. Gene expression subgroups may represent distinct types of disease.

Methods

Eighty-seven cases of supratentorial oligodendroglioma were selected from 145 cases treated in a single center between January 1990 and December 2001. Fluorescence in situ hybridization was used to determine the status of chromosomes 1p and 19q. Parameters evaluated included clinical data and radiological and histological features. Univariate and multivariate analyses were performed and a probability value less than 0.05 was considered significant.

The patients included 48 women and 39 men. The overall mean age at presentation was 45 years for women and 36 years for men (p = 0.006). The univariate analysis identified the following as favorable prognostic factors: younger patient age (p = 10−5), female sex (p = 0.0025), seizure as a presenting symptom (p = 10−5), normal clinical examination (p = 10−5), absence of lesion enhancement on neuroimaging studies (p = 0.0231), lack of histological necrosis (p = 0.0003), absence of mitoses (p = 0.0014), 1p and 19q deletions (p = 0.0001), absence of recurrence (p = 0.0021), and adjuvant radiotherapy and/or chemotherapy (p = 10−5). The multivariate analysis identified patient age (p = 10−5) and chromosomal anomalies (p = 0.002) as independently linked to survival. Three molecular subtypes emerged: oligodendroglioma with 1p and 19q deletions, oligodendroglioma demonstrating polysomia and a lack of meaningful response to radiotherapy or chemotherapy, and oligodendroglioma with no 1p-9q deletion in which partial response was seen.

Conclusions

According to our data, oligodendrogliomas could be divided into three molecular subtypes. Although chemotherapy seems efficient for managing this tumor, additional studies should be conducted to compare the efficacy of radiotherapy and chemotherapy.

Molecular diagnostics in central nervous system tumors

Central nervous system (CNS) neoplasms can be diagnostically challenging, due to remarkably wide ranges in histologic appearance, biologic behavior, and therapeutic approach. Nevertheless, accurate diagnosis is the critical first step in providing optimal patient care. As with other oncology-based specialties, there is a rapidly expanding interest and enthusiasm for identifying and utilizing new biomarkers to enhance the day-to-day practice of surgical neuropathology. In this regard, the field is primed by recent advances in basic research, elucidating the molecular mechanisms of tumorigenesis and progression in the most common adult and pediatric brain tumors. Thus far, few have made the transition into routine clinical practice, the most notable example being 1p and 19q testing in oligodendroglial tumors. However, the field is rapidly evolving and many other biomarkers are likely to emerge as useful ancillary diagnostic, prognostic, or therapeutic aids. The goal of this article is to highlight the most common genetic alterations currently implicated in CNS tumors, focusing most on those that are either already in common use in ancillary molecular diagnostics testing or are likely to become so in the near future.