Methods
Following Institutional Review Board approval, the pathology and
clinical database was queried for cases of myxopapillary ependymoma
(MPE) occurring in patients less than 18 years of age diagnosed or
treated at our institution between 1996 and 2018. The electronic medical
record was reviewed for pertinent clinical data. The slides for
available cases were reviewed, and histologic information was collected
from the microscopic descriptions of the internally generated slide
reviews of the other cases. Histologically, each case was evaluated for
overall cellularity, mitotic activity, necrosis, microvascular
proliferation, presence of an identifiable capsule, leptomeningeal
involvement, and nerve root involvement. Immunohistochemical studies for
H3K27me3 (C36B11 clone; Cell Signaling) and chromosomal microarray
analysis were performed on all cases with available tissue (5 of 8
cases).
The OncoScan® FFPE Assay Kit (Thermo Fisher Scientific; Santa Clara, CA)
was applied to isolated DNA. The technicalities of the molecular
inversion probe (MIP) assay have been previously described.18 The genome-wide functional resolution of this array
is approximately 500 kilobases for non-mosaic deletions and non-mosaic
duplications. Deletions larger than 1 megabase, duplications larger than
2 megabases, and copy neutral loss of heterozygosity (cnLOH) larger than
10 megabases are generally reported. As a caveat, the functional
resolution of this array varies significantly dependent upon size of the
abnormality, probe density in region, percentage of abnormal cells, and
quality of the DNA obtained, and mosaic clonal abnormalities, especially
those that are represented in a minor fraction of the sample, may not be
detected. . All data were analyzed and reported using the February 2009
NCBI human genome build 37.1 (hg19). The genome coordinates described
are best estimates and may not represent precise breakpoints, especially
for abnormalities detected in a low percentage of cells.