Comprehensive profiling of myxopapillary ependymomas identifies a distinct molecular subtype with relapsing disease

Myxopapillary ependymoma is a heterogeneous disease with respect to histopathology and clinical outcome. However, there are no diagnostic markers or clinical parameters that reliably predict the progression-free survival of the respective patients. We analyzed 185 tumors that classified as myxopapillary ependymoma based on global DNA methylation. Of these, 46 samples have been previously analyzed in GSE65362, GSE90496 or GSE109381. Using k-means clustering, our series split up into two distinct subtypes: MPE-A occurred in younger patients (median age 27 years) and were significantly enriched with tumors demonstrating papillary morphology and MGMT promoter methylation. Half of these tumors could not be totally resected, and 85% relapsed within 10 years. On the other hand, MPE-B occurred at a median age of 45 years. They included a significantly higher number of tumors with an initial diagnosis of WHO grade II and tanycytic morphology. Importantly, patients within this subgroup had a significantly better outcome with a relapse rate of only 33% in 10 years. 185 specimens were analyzed using the Illumina Infinium HumanMethylation450 or the MethylationEPIC BeadChip.