A simple algorithmic approach using histology and immunohistochemistry for the current classification of adult diffuse glioma in a resource-limited set-up

Pathological Evaluation of Diffuse Gliomas Using IDH1 and ATRX in a Resource-Limited Setting

INTRODUCTION

Classification of gliomas based on tumor histology remains the gold standard in the diagnosis and prognosis of gliomas. However, the recent World Health Organization (WHO) classification has included molecular studies for diagnosis and prognostication. Immunohistochemical markers such as isocitrate dehydrogenase 1 (IDH1) and alpha thalassemia/mental retardation syndrome X-linked (ATRX) can be used for the diagnosis and prognosis of the majority of gliomas.

OBJECTIVES

We aim to study the frequencies of IDH1 and ATRX mutations in diffuse gliomas using surrogate immunohistochemical markers and correlate histopathological findings of gliomas with immunohistochemical findings.

MATERIAL AND METHODS

This was a retrospective study of one-year duration from January 2022 to December 2022, conducted in the department of pathology. Relevant data was retrieved from medical records. Histopathology blocks were collected and sent for immunohistochemical studies using tissue microarray for IDH1 and ATRX.

STATISTICAL ANALYSIS

Qualitative data were expressed in percentages and proportions. The difference in proportion was calculated using the chi-square test, and a p-value of <0.005 was taken as significant.

RESULTS

A total of 51 cases of diffuse gliomas were included in the study. The frequency of IDH1-positive diffuse astrocytomas was 33 (64.7%), and loss of ATRX was seen in 12 (23.5%) cases.

CONCLUSION

Immunohistochemistry serves as a surrogate marker to detect molecular alterations in diffuse gliomas.

Molecular Biomarker Testing for the Diagnosis of Diffuse Gliomas

CONTEXT.—

The diagnosis and clinical management of patients with diffuse gliomas (DGs) have evolved rapidly over the past decade with the emergence of molecular biomarkers that are used to classify, stratify risk, and predict treatment response for optimal clinical care.

OBJECTIVE.—

To develop evidence-based recommendations for informing molecular biomarker testing for pediatric and adult patients with DGs and provide guidance for appropriate laboratory test and biomarker selection for optimal diagnosis, risk stratification, and prediction.

DESIGN.—

The College of American Pathologists convened an expert panel to perform a systematic review of the literature and develop recommendations. A systematic review of literature was conducted to address the overarching question, "What ancillary tests are needed to classify DGs and sufficiently inform the clinical management of patients?" Recommendations were derived from quality of evidence, open comment feedback, and expert panel consensus.

RESULTS.—

Thirteen recommendations and 3 good practice statements were established to guide pathologists and treating physicians on the most appropriate methods and molecular biomarkers to include in laboratory testing to inform clinical management of patients with DGs.

CONCLUSIONS.—

Evidence-based incorporation of laboratory results from molecular biomarker testing into integrated diagnoses of DGs provides reproducible and clinically meaningful information for patient management.

Grading of adult diffuse gliomas according to the 2021 WHO Classification of Tumors of the Central Nervous System

The grading of gliomas based on histological features has been a subject of debate for several decades. A consensus has not yet been reached because of technical limitations and inter-observer variations. While the traditional grading system has failed to stratify the risk of IDH-mutant astrocytoma, canonical histological and proliferative markers may be applicable to the risk stratification of IDH-wild-type astrocytoma. Numerous studies have examined molecular markers in order to obtain more clinically relevant information that will improve the risk stratification of gliomas. The CDKN2A/B homozygous deletion for IDH-mutant astrocytoma and the following three criteria for IDH-wild-type astrocytoma: the concurrent gain of whole chromosome 7 and loss of whole chromosome 10, TERT promoter mutations, and EGFR amplification, were identified as independent molecular markers of the worst clinical outcomes. Therefore, the 2021 World Health Organization (WHO) Classification of Tumors of the Central Nervous System adopted these molecular markers into the revised grading criteria of IDH-mutant and -wild-type astrocytoma, respectively, as a grading system within tumor types. Of note, several recent studies have shown that some low-grade IDH-wild-type astrocytoma lacking both the molecular glioblastoma signature and genetic alterations typical of pediatric-type gliomas may demonstrate a relatively indolent clinical course, suggesting the existence of lower-grade adult IDH-wild-type astrocytoma. In terms of oligodendroglioma, IDH-mutant, and 1p/19q codeleted, consistent makers that predict poor outcomes have not yet been identified, and, thus, the current criteria have remained unchanged. Molecular testing to fulfill the revised WHO criteria is, however, not always available worldwide, and in that case, an integrated diagnosis combining all available complementary information is highly recommended. This review discusses controversial issues surrounding legacy grading systems and newly identified potential genetic markers of adult diffuse gliomas and provides perspectives on future grading systems.

Clinical, Morphological, and Molecular Study of Diffuse WHO Grade II and III Astrocytomas: A Retrospective Analysis from a Single Tertiary Care Institute

Introduction Astrocytomas are the most common gliomas, classified on the basis of grade and IDH mutation status according to the World Health Organization (WHO) 2016 update. IDH mutations are seen in 70 to 80% of diffuse grade II and III astrocytomas and are associated with better outcome. They serve as predictive biomarker in IDH-targeted therapies such as small-molecule inhibitors or vaccines.

Objective The aim of this study was to analyze the clinical, morphological, immunohistochemical, and molecular genetic characteristics of diffuse astrocytoma (DA: grades II and III). The IDH mutant and wild-type tumors are compared and contrasted with survival analysis on follow-up.

Materials and Methods This was a retrospective study conducted on surgically resected tumor specimens. The hematoxylin and eosin-stained slides were examined for histologic features. Immunohistochemistry (IHC) was performed using IDH1R132H, ATRX, p53, and Ki67. All cases of negative immunohistochemical expression of IDH1R132H were subjected to IDH1 mutation analysis by Sanger sequencing. Overall survival was estimated by the Kaplan-Meier method using the log-rank (Mantel–Cox) test.

Results The study included 51 cases of DA in the age of 17 to 66 years, mean ± standard deviation was 35.5 ± 9.7 years, and male:female ratio was 2:1.The IDH1R132H cytoplasmic immunopositivity was seen in 36 cases (70.5%), of which 63.6% were of grade II and 72.5% were of grade III. ATRX showed loss of expression in 50 cases (98%), and p53 showed diffuse strong immunohistochemical expression in all the cases of IDH mutant tumors. The difference in the age at presentation for IDH mutant (32.5 years) and wild type tumors (38 years) was statistically significant. Median survival was 55.3 months and 22.2 months in of IDH mutant and wild type cases, respectively.

Conclusion IHC and sequencing for IDH mutations is helpful in making an integrated diagnosis and classifying definite molecular subgroups of astrocytic tumors. Mutations in IDH core-elate with survival. IDH mutant tumors showed longer survival duration and are good prognostic indicators.

Reliability of IDH1-R132H and ATRX and/or p53 immunohistochemistry for molecular subclassification of Grade 2/3 gliomas

Since the World Health Organization 2016 classification (2016 WHO), genetic status has been incorporated into the diagnosis of Grade 2/3 gliomas (lower-grade gliomas). Therefore, immunohistochemistry (IHC) of IDH1-R132H, ATRX, and p53 have been used in place of genetic status. We report the associations between histological findings, IHC, and genetic status. We performed IHC of IDH1-R132H, ATRX, and p53 in 76 lower-grade gliomas and discussed its validity based on the 2016 WHO and the upcoming 2021 WHO classification. The sensitivity and specificity of anti-ATRX, p53, and IDH1-R132H IHC were 40.9%/98.1%, 78.6%/85.4%, and 90.5%/84.6%, respectively. Among 21 IDH1-mutant gliomas without 1p/19q codeletion, two gliomas (9.5%) mimicked the so-called classic for oligodendroglioma (CFO) in their morphology. Of the 42 gliomas with 1p/19q codeletion, four cases were difficult to diagnose as oligodendroglioma through morphological examination. Moreover, there were three confusing cases with ATRX mutations but with retained ATRX-IHC positivity. The lessons learned from this study are as follows: (1) ATRX-IHC and p53-IHC should be supplementary to morphological diagnosis, (2) rare IDH mutations other than IDH1 R132H should be considered, and (3) there is no complete alternative test to detect molecular features of glioblastoma under the 2021 WHO classification.

Subgroup stratification of adult diffuse gliomas and outcomes: an adaptation of the updated WHO classification in a resource-constrained environment

Introduction:

The updated World Health Organization 2016 classification of central nervous system tumours recommends the addition of molecular parameters to histological diagnosis. In a resource-constrained setting, molecular testing such as gene sequencing and fluorescence in situ hybridisation is not feasible for all the patients. We assessed the utility of immunohistochemistry (IHC) for isocitrate dehydrogenase (IDH1/R132H) gene and alpha thalassemia/mental retardation syndrome X linked gene (ATRX) to stratify adult diffuse gliomas into subgroups and analysed the outcomes.

Materials/Methods:

Fifty-eight patients with grades III/IV astrocytic gliomas were tested by IHC for IDH1/R132H and ATRX mutation as per the standard protocol and were later stratified into three subgroups based on IHC. IDH1/R132H positive/ATRX retained gliomas were stratified as group 1 (G1), IDH1/R132H positive/ATRX lost were grouped as G2 and IDH1/R132H negative (with or without ATRX loss) as G3. All patients underwent adjuvant therapy as per the Stupp regimen. Outcomes and survival were analysed by Kaplan–Meier analysis using SPSS 21.v.

Results:

Median age of the cohort of 58 patients (male: 39, female: 19) was 40 years. Histologically, glioblastoma multiforme (GBM), anaplastic astrocytoma (AA) and anaplastic oligodendroglioma (AOD) were seen in 23:17:18 patients. Forty-eight percent were tested positive for IDH1/R132H, 62% had retained ATRX protein stratifying patients into three subgroups (G1:14, G2:14, G3:30). The G3 group contained both AA and GBM cases. At median follow-up of 18 months, overall survival (OS) of the entire cohort was 76%, higher in G1, compared to G2 and G3 (log-rank p = 0·01). In comparison to various factors such as age, gender, location of the lesion and presenting symptom on survival among various groups, we found that gender of the patient in group I (men vs. women, p = 0·02), laterality of the tumour in group II (right vs. left, p = 0·07) and age of the patient in group III (<45 vs. >45, p = 0·01) demonstrated significant impact on OS.

Conclusion:

Subgroup stratification of adult diffuse gliomas based on IHC for IDH/R132H and ATRX demonstrates that group 1 was the most favourable prognostic factor. In a resource-constrained environment, IHC alone may guide appropriate management decision for the majority of adult diffuse gliomas, gene sequencing reserved for IDH1/R132H negative GBM in patients less than 45 years of age.

IDH1, ATRX, and BRAFV600E mutation in astrocytic tumors and their significance in patient outcome in north Indian population

Background:

According to the current World Health Organization (WHO) classification of central nervous system (CNS) tumors (2016), histological diagnosis of gliomas should be supplemented by molecular information. This study was carried out to determine the frequency of isocitrate dehydrogenase 1 (IDH1), ATRX, and BRAF V600E mutations in different grade astrocytomas and their prognostic value.

Methods:

Eighty cases of astrocytoma (15 pilocytic astrocytoma, 25 diffuse astrocytoma, 15 anaplastic astrocytoma, and 25 glioblastoma) with follow-up information were analyzed using immunohistochemistry for IDH1 mutant protein, ATRX, p53, and BRAF. Sanger sequencing was carried out for IDH1 exon 4 and BRAF exon 15.

Results:

All pilocytic astrocytoma and primary glioblastoma cases were negative for IDH1 mutation. IDH1 mutation was detected in 80% (20/25) DA and 87% (13/15) AA cases. IDH1 R132H was the commonest IDH1 mutation (94.1%) and immunohistochemistry showed 100% sensitivity and specificity to detect this mutation. Loss of nuclear ATRX expression was found in 87% (20/23) and 100% (14/14) DA and AA cases, respectively. IDH1 mutant DA patients had longer overall survival than IDH1 wild cases, although this difference was not significant (79.5 months vs. 42.5 months, P value 0.417). BRAF V600E mutation was not detected in any astrocytic tumor.

Conclusions:

IDH1 and ATRX mutations are very common in diffuse astrocytoma and anaplastic astrocytoma, while they are rare in pilocytic astrocytoma and glioblastoma. Immunohistochemistry for IDH1 and ATRX can successfully characterize the diffuse gliomas into molecularly defined groups in majority of the cases. BRAF V600E mutation is rare in astrocytic tumors in Indian population.