Ependymomas are
gliomas that recapitulate normal ependymal cells. The
epithelial membrane antigen (EMA) shows "dot-like" and "ring-like" staining patterns, highlighting "microlumens" or intracytoplasmic rosettes, a pathognomonic ultrastructural feature. NHERF1/EBP50, an adaptor
protein localized at the apical plasma membrane of human epithelia, has been found to localize to these microlumens. We aimed to analyze the staining patterns of EMA and EBP50 in
ependymomas and other
tumors, and thereby compare their diagnostic utility. Sixty-three
ependymomas of different grades and 44 nonependymal
tumors (
meningiomas, 5;
pilocytic astrocytoma, 2;
paraganglioma, 2;
neurocytoma, 4;
pituitary adenoma, 3; papillary
tumor of pineal region, 3;
oligodendroglioma, 4;
choroid plexus papilloma, 3;
medulloblastoma, 2;
schwannoma, 2; cellular
hemangioblastoma, 2;
subependymal giant cell astrocytoma, 1;
glioblastoma multiforme, 8; diffuse
astrocytoma, 1;
anaplastic astrocytoma, 1; and pilomyxoid
astrocytoma, 1) were included. Ring-like positivity was 100% specific for
ependymomas, but showed a poor sensitivity (EMA, 29%; EBP50, 37%). Dot EMA positivity was more sensitive in grade III
ependymomas (100%), whereas dot EBP50 positivity was more sensitive in grade I
subependymomas (80%) and
myxopapillary ependymomas (40%). Among grade II
ependymomas, EBP50 labeled a significantly higher number of dots and rings, which may be of value in small biopsies. Focal dot positivity for EMA and EBP50 in
glioblastoma multiforme and
meningioma contributed to the lowered specificity (EMA, 84%; EBP50, 80%).
Myxopapillary ependymomas (60%),
choroid plexus papillomas (66%), and papillary
tumors of pineal region (100%) showed membranous staining with EBP50. Although EPB50 appears to be a better diagnostic marker for grade I/II
ependymomas, we recommend a combined panel of EMA and EBP50 for grade III
ependymomas to compensate for the reduced sensitivity of EBP50 in this subgroup.