[Criteria of diagnosis and grading of oligodendrogliomas or oligo-astrocytomas according to the WHO and Sainte-Anne classifications]

Clinical applications of arterial spin labeling

MR arterial spin labeling is primarily applied as a neuroimaging method to measure cerebral blood flow. As this technique becomes more widely available, a basic understanding of the clinical applications is necessary for optimal utilization in the setting of patient care. This review focuses on the use of arterial spin labeling imaging for the evaluation of cerebrovascular disease, brain tumors and neuropsychiatric illness.

Can dynamic contrast-enhanced magnetic resonance imaging combined with texture analysis differentiate malignant glioneuronal tumors from other glioblastoma?

An interesting approach has been proposed to differentiate malignant glioneuronal tumors (MGNTs) as a subclass of the WHO grade III and IV malignant gliomas. MGNT histologically resemble any WHO grade III or IV glioma but have a different biological behavior, presenting a survival twice longer as WHO glioblastomas and a lower occurrence of metastases. However, neurofilament protein immunostaining was required for identification of MGNT. Using two complementary methods, dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and texture analysis (MRI-TA) from the same acquisition process, the challenge is to in vivo identify MGNT and demonstrate that MRI postprocessing could contribute to a better typing and grading of glioblastoma. Results are obtained on a preliminary group of 19 patients a posteriori selected for a blind investigation of DCE T1-weighted and TA at 1.5 T. The optimal classification (0/11 misclassified MGNT) is obtained by combining the two methods, DCE-MRI and MRI-TA.

[Grading of adults primitive glial neoplasms using arterial spin-labeled perfusion MR imaging]

PURPOSE

We investigated the relationship between tumor blood-flow measurement based on perfusion-imaging by arterial spin-labeling (ASL) and histopathologic findings in adults' primitive glial tumours.

PATIENTS AND METHODS

Thus, 40 primitive brain tumors (8 low-grade and 32 high-grade gliomas according to the Sainte-Anne classification) were imaged using pulsed (n=19) or continuous (n=21) ASL. Relative cerebral blood flow (rCBF=tumoral blood flow/normal cerebral blood flow) between high- and low-grade gliomas were compared.

RESULTS

Using pulsed ASL, differences in mean rCBF were observed in high- and low-grade gliomas although no significant (respectively 1.95 and 1.5). Using continuous ASL, mean rCBF were significantly higher for high-grade than for low-grade gliomas (P<0.05). High-grade gliomas could be discriminated using a CBF threshold of 1.18, with a sensitivity of 88%, specificity of 60%, predictive positive value of 88%, and predictive negative value of 60%.

CONCLUSION

ASL-based perfusion provides a quantitative, non-invasive alternative to dynamic susceptibility contrast perfusion MR methods for evaluating CBF. ASL is a suitable method for gliomas initial staging and could be useful to identify intermediate tumoral evolution.

Clinical relevance of tumor cells with stem-like properties in pediatric brain tumors

Background

Primitive brain tumors are the leading cause of cancer-related death in children. Tumor cells with stem-like properties (TSCs), thought to account for tumorigenesis and therapeutic resistance, have been isolated from high-grade gliomas in adults. Whether TSCs are a common component of pediatric brain tumors and are of clinical relevance remains to be determined.

Methodology/Principal Findings

Tumor cells with self-renewal properties were isolated with cell biology techniques from a majority of 55 pediatric brain tumors samples, regardless of their histopathologies and grades of malignancy (57% of embryonal tumors, 57% of low-grade gliomas and neuro-glial tumors, 70% of ependymomas, 91% of high-grade gliomas). Most high-grade glioma-derived oncospheres (10/12) sustained long-term self-renewal akin to neural stem cells (>7 self-renewals), whereas cells with limited renewing abilities akin to neural progenitors dominated in all other tumors. Regardless of tumor entities, the young age group was associated with self-renewal properties akin to neural stem cells (P = 0.05, chi-square test). Survival analysis of the cohort showed an association between isolation of cells with long-term self-renewal abilities and a higher patient mortality rate (P = 0.013, log-rank test). Sampling of low- and high-grade glioma cultures showed that self-renewing cells forming oncospheres shared a molecular profile comprising embryonic and neural stem cell markers. Further characterization performed on subsets of high-grade gliomas and one low-grade glioma culture showed combination of this profile with mesenchymal markers, the radio-chemoresistance of the cells and the formation of aggressive tumors after intracerebral grafting.

Conclusions/Significance

In brain tumors affecting adult patients, TSCs have been isolated only from high-grade gliomas. In contrast, our data show that tumor cells with stem cell-like or progenitor-like properties can be isolated from a wide range of histological sub-types and grades of pediatric brain tumors. They suggest that cellular mechanisms fueling tumor development differ between adult and pediatric brain tumors.