Podoplanin is a potential marker for the diagnosis of ependymoma: a comparative study with epithelial membrane antigen (EMA).

Podoplanin is a mucin-type transmembrane sialoglycoprotein that is characteristically expressed in lymphatic endothelia. It is also expressed in the ependyma of the central nervous system as well as in ependymomas. Particularly, membrane-bound structures along the luminal surface, ring-like structures, and dot-like structures in the cytoplasm, all of which were originally reported for epithelial membrane antigen (EMA) immunohistochemistry in ependymoma, were also reported for podoplanin immunohistochemistry in ependymoma. This study was undertaken to evaluate podoplanin as compared with EMA as a marker of ependymoma. A total of 16 ependymomas (WHO Grade (G) II, 9 cases; GIII, 4; myxopapillary, 2; GIII clear cell, (1) were immunohistochemically studied using antibodies against podoplanin (clones D2-40 and NZ-1) as well as an antibody against EMA (clone E29). In all cases, D2-40 and NZ-1 excellently labeled linear signals along the luminal surface of ependymal canals/rosettes, dot-like structures, and/or ringlike structures, as did E29. These structures were generally more abundant in GII ependymomas than in GIII ependymomas. A semiquantitative analysis between the immunopositive structures of D2-40 or NZ-1 and E29 was conducted with a focus on the dot-like structures and the ring-like structures in the cases of GII and GIII ependymoma. The result showed that there was no statistical difference between D2-40 or NZ-1 and E29. Our study suggests that podoplanin is a potential marker for the diagnosis of ependymoma that corresponds to EMA. Anti-podoplanin antibodies and anti-EMA antibodies could cooperate with each other for the diagnostic immunohistochemistry of ependymoma.