Proliferative activity and histopathological features in diffuse grade II astrocytomas

Update for astrocytomas: medical and surgical management considerations

Astrocytomas include a wide range of tumors with unique mutations and varying grades of malignancy. These tumors all originate from the astrocyte, a star-shaped glial cell that plays a major role in supporting functions of the central nervous system (CNS), including blood-brain barrier (BBB) development and maintenance, water and ion regulation, influencing neuronal synaptogenesis, and stimulating the immunological response. In terms of epidemiology, glioblastoma (GB), the most common and malignant astrocytoma, generally occur with higher rates in Australia, Western Europe, and Canada, with the lowest rates in Southeast Asia. Additionally, significantly higher rates of GB are observed in males and non-Hispanic whites. It has been suggested that higher levels of testosterone observed in biological males may account for the increased rates of GB. Hereditary syndromes such as Cowden, Lynch, Turcot, Li-Fraumeni, and neurofibromatosis type 1 have been linked to increased rates of astrocytoma development. While there are a number of specific gene mutations that may influence malignancy or be targeted in astrocytoma treatment, O 6-methylguanine-DNA methyltransferase (MGMT) gene function is an important predictor of astrocytoma response to chemotherapeutic agent temozolomide (TMZ). TMZ for primary and bevacizumab in the setting of recurrent tumor formation are two of the main chemotherapeutic agents currently approved in the treatment of astrocytomas. While stereotactic radiosurgery (SRS) has debatable implications for increased survival in comparison to whole-brain radiotherapy (WBRT), SRS demonstrates increased precision with reduced radiation toxicity. When considering surgical resection of astrocytoma, the extent of resection (EoR) is taken into consideration. Subtotal resection (STR) spares the margins of the T1 enhanced magnetic resonance imaging (MRI) region, gross total resection (GTR) includes the margins, and supramaximal resection (SMR) extends beyond the margin of the T1 and into the T2 region. Surgical resection, radiation, and chemotherapy are integral components of astrocytoma treatment.

An Updated Comparison Between World Health Organization Grade II Gemistocytic and Diffuse Astrocytoma Survival and Treatment Patterns

BACKGROUND

In 2016, the World Health Organization revised its guidelines to retain only gemistocytic astrocytoma (GemA) as a distinct variant of diffuse astrocytoma (DA). In the past, grade II GemAs were linked with a worse prognosis than DA. However, it is unclear how consistently the tumor subtype has been diagnosed over time. We used more recent data to compare outcomes between grade II GemA and DA.

METHODS

Patients with grade II DA and GemA were extracted from the Surveillance, Epidemiology, and End Results database between 1973 and 2016. Kaplan-Meier curves estimated survival differences across different eras, with a focus on patients diagnosed between 2000 and 2016, and propensity score matching was used to balance baseline characteristics between DA and GemA cohorts.

RESULTS

Of 2467 patients with grade II astrocytoma diagnosed between 2000 and 2016, 132 (5.35%) had GemA, and 2335 (94.65%) had DA. At baseline, marked demographic and treatment differences were noted between tumor subtypes, including age at diagnosis and female sex. GemA patients did not have worse survival compared with DA patients at baseline (P = 0.349) or after propensity score matching (P = 0.497). Multivariate Cox models found that surgical extent of resection was associated with a survival benefit for DA patients, and both DA and GemA patients >65 years old had dramatically inferior survival.

CONCLUSIONS

Our data suggest that the impact of GemA versus DA histopathology depends more on the decade of queried data rather than patient-specific demographics. Using more recent longitudinal data, we found that grade II GemA and DA tumors did not have significant differences in survival. These data may prove useful for clinicians counseling patients with grade II GemA.

The histological representativeness of glioblastoma tissue samples

Background

Glioblastomas (GBMs) are known for having a vastly heterogenous histopathology. Several studies have shown that GBMs can be histologically undergraded due to sampling errors of small tissue samples. We sought to explore to what extent histological features in GBMs are dependent on the amount of viable tissue on routine slides from both biopsied and resected tumors.

Methods

In 106 newly diagnosed GBM patients, we investigated associations between the presence or degree of 24 histopathological and two immunohistochemical features and the tissue amount on hematoxylin-eosin (HE) slides. The amount of viable tissue was semiquantitatively categorized as “sparse,” “medium,” or “substantial” for each case. Tissue amount was also assessed for associations with MRI volumetrics and the type of surgical procedure.

Results

About half (46%) of the assessed histological and immunohistochemical features were significantly associated with tissue amount. The significant features were less present or of a lesser degree when the tissue amount was smaller. Among the significant features were most of the features relevant for diffuse astrocytic tumor grading, i.e., small necroses, palisades, microvascular proliferation, atypia, mitotic count, and Ki-67/MIB-1 proliferative index (PI).

Conclusion

A substantial proportion of the assessed histological features were at risk of being underrepresented when the amount of viable tissue on HE slides was limited. Most of the grading features were dependent on tissue amount, which underlines the importance of considering sampling errors in diffuse astrocytic tumor grading. Our findings also highlight the importance of adequate tissue collection to increase the quality of diagnostics and histological research.

Prognostic value of survivin and DNA topoisomerase IIα in diffuse and anaplastic astrocytomas

Distinguishing WHO grade II astrocytomas from grade III is a difficult task. This study looks into the potential prognostic use of mitotic activity and the proliferation markers Ki67/MiB-1 (Ki67), survivin and DNA topoisomerase IIα (TIIα) in 59 WHO grade II diffuse astrocytomas (DA) and 33 WHO grade III anaplastic astrocytomas (AA), IDH1 R132H-mutated and not otherwise specified (NOS) by means of immunohistochemistry. All proliferation markers showed higher expression in AA compared with DA. Only Ki67 had significantly greater expression in astrocytomas, NOS vs. astrocytomas, IDH1-mutated. Uni-/multivariable COX-regression analyses showed that greater expression of both survivin and TIIα were associated with poorer survival when stratified for IDH1-mutation status and, additionally, achieved hazard rates surpassing clinically established prognostic factors such as age and WHO performance status. Ki67 achieved only statistical significance in univariable analyses, whereas mitoses did not reveal any relation to survival. IDH1-mutated astrocytomas had significantly better survival than astrocytomas, NOS. Among IDH1-mutated astrocytomas no significant difference in survival was shown between DA and AA. Our findings suggest a potential usefulness of proliferation markers in the prognostic setting of astrocytomas independent of IDH1-mutation status, and survivin and TIIα are potential candidates in that regard.

Protoplasmic astrocytoma with multifocal involvement: case report and radiological findings

Protoplasmic astrocytomas are a poorly characterized and extremely rare subtype of astrocytoma. We describe the CT, MR and ¹⁸F-fludeoxyglucose positron emission tomography (FDG-PET) findings of a multifocal protoplasmic astrocytoma in a 29-year-old male with neurological deficits. He was initially diagnosed with neurosarcoidosis based on imaging. MRI demonstrated intraparenchymal lesions involving the right temporal lobe and cerebellum. These appeared as extremely hyperintense signals on T₂ weighted imaging and as homogeneous enhancements with a small non-enhancing cystic component on contrast-enhanced MR. Diffuse post-contrast enhancement of the craniospinal meninges was also noted. Post-radiation therapy PET-CT demonstrated a highly FDG-avid tumour in the right temporal lobe and left cerebellum. To our knowledge, a multifocal form of protoplasmic astrocytoma in an adult patient has not been previously described.

Low-grade astrocytomas: the prognostic value of fibrillary, gemistocytic, and protoplasmic tumor histology

OBJECT

Low-grade astrocytomas are slow-growing, infiltrative gliomas that over time may progress into more malignant tumors. Various factors have been shown to affect the time to progression and overall survival including age, performance status, tumor size, and the extent of resection. However, more recently it has been suggested that histological subtypes (fibrillary, protoplasmic, and gemistocytic) may impact patient outcome. In this study the authors have performed a large comparative population-based analysis to examine the characteristics and survival of patients with the various subtypes of WHO Grade II astrocytomas.

METHODS

Patients diagnosed with fibrillary, protoplasmic, and gemistocytic astrocytomas were identified through the Surveillance, Epidemiology, and End Results (SEER) database. The chi-square test and Student t-test were used to evaluate differences in patient and treatment characteristics between astrocytoma subtypes. Kaplan-Meier analysis was used to assess overall survival, and the log-rank test was used to evaluate the differences between survival curves. Univariate and multivariate analyses were also performed to determine the effect of various patient, tumor, and treatment variables on overall survival.

RESULTS

A total of 500 cases were included in the analysis, consisting of 326 fibrillary (65.2%), 29 protoplasmic (5.8%), and 145 gemistocytic (29%) variants. Gemistocytic astrocytomas presented at a significantly older age than the fibrillary variant (46.8 vs 37.7 years, p < 0.0001), with protoplasmic and fibrillary subtypes having a similar age. Although protoplasmic and fibrillary variants underwent radiotherapy at similar rates, gemistocytic tumors more frequently received radiotherapy (p = 0.0001). Univariate analysis revealed older age, larger tumor size, and the use of radiotherapy to be poor prognostic factors, with resection being associated with improved survival. The gemistocytic subtype (hazard ratio [HR] 1.62 [95% CI 1.27-2.07], p = 0.0001) also resulted in significantly worse survival than fibrillary tumors. Bivariate analyses demonstrated that older age, the use of radiotherapy, and resection significantly influenced median survival. Tumor subtype also affected median survival; patients who harbored gemistocytic tumors experienced less than half the median survival of fibrillary and protoplasmic tumors (38 vs 82 months, p = 0.0003). Multivariate analysis revealed increasing age (HR 1.05 [95% CI 1.04-1.05], p < 0.0001), larger tumor size (HR 1.02 [95% CI 1.01-1.03], p = 0.0002), and the use of resection (HR 0.70 [95% CI 0.52-0.94], p = 0.018) to be independent predictors of survival. Examination of tumor subtype revealed that the gemistocytic variant (HR 1.30 [95% CI 0.98-1.74], p = 0.074) was associated with worse patient survival than fibrillary tumors, although this only approached significance. The protoplasmic subtype did not affect overall survival (p = 0.33).

CONCLUSIONS

Gemistocytic tumor histology was associated with worse survival than fibrillary and protoplasmic astrocytomas. As protoplasmic astrocytomas have a survival similar to fibrillary tumors, there may be limited utility to the identification of this rare variant. However, increased attention should be paid to the presence of gemistocytes in low-grade gliomas as this is associated with shorter time to progression, increased malignant transformation, and reduced overall survival.

Expression and clinical significance of the proliferation marker minichromosome maintenance protein 2 (Mcm2) in diffuse astrocytomas WHO grade II

Background

The WHO classification system for astrocytomas is not considered optimal, mainly because of the subjective assessment of the histopathological features. Few prognostic variables have been found that stratify the risk of clinical progression in patients with grade II astrocytoma. For that reason there is a continuous search for biomarkers that can improve the histopathological diagnosis and prognostication of these tumours.

Aim

This study was designed to investigate the prognostic significance of the proliferative marker Mcm2 (minichromosome maintenance protein 2) in diffuse astrocytomas WHO grade II and correlate the findings with histopathology, mitoses, and Ki67/MIB-1 immunostaining.

Method

61 patients with histologically verified grade II astrocytoma (WHO 2007) were investigated. Paraffin sections were immunostained with anti-Mcm2, and the Mcm2 proliferative index (PI) was determined as the percentage of immunoreactive tumour cell nuclei.

Results

Mcm2 PI was not associated with any histopathological features but correlated significantly with mitotic count and Ki67/MIB-1 PI (p<0.05). In the survival analyses Mcm2 showed trends to poorer survival, however, statistical significance was not achieved in the univariate analyses (p>0.05).

Conclusions

In our hands Mcm2 immunostaining has no advantage over Ki67/MIB-1 in the evaluation of grade II astrocytomas. Larger studies are needed to fully clarify the prognostic role of this biomarker.

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1715002791944037