Anatomic Neuroimaging Characteristics of Posterior Fossa Type A Ependymoma Subgroups

Area of Science:

• Neuro-oncology
• Molecular biology
• Radiology

Background:

• Posterior fossa type A (PFA) ependymomas are classified into two molecular subgroups, PFA-1 and PFA-2, with distinct developmental origins suggested by gene expression profiling.
• These subgroups may exhibit different anatomical characteristics on MR imaging.

Purpose of the Study:

• To investigate whether PFA-1 and PFA-2 ependymomas display different anatomical features on preoperative MR imaging.
• To correlate MR imaging characteristics with molecular subgroups and subtypes of PFA ependymomas.

Main Methods:

• Two neuroradiologists reviewed MR imaging of 122 PFA ependymomas, assessing features like ventricular foramina extension and arterial encasement.
• Tumors were molecularly classified into PFA-1 or PFA-2 using DNA methylation profiling.
• Associations between imaging variables and molecular subgroups/subtypes were analyzed.

Main Results:

• No significant association was found between MR imaging variables and the PFA-1 or PFA-2 subgroups.
• A specific subtype, PFA-2c, exhibited a more circumscribed MR imaging appearance.
• PFA-2c ependymomas showed a reduced tendency for fourth ventricular foramina extension and blood vessel encasement compared to other subtypes.

Conclusions:

• The study does not support the hypothesis that PFA-1 and PFA-2 ependymomas have distinct anatomical origins based on MR imaging.
• PFA-2c ependymomas may have a more anatomically circumscribed MR imaging appearance, warranting further investigation in larger cohorts.