[Immunohistochemical study for choroid plexus papillomas and ependymomas].

An immunohistochemical study of glial fibrillary acidic protein (GFAP), S-100 protein, cytokeratin (CKER), epithelial membrane antigen (EMA), and transthyretin (TTR) was carried out on 11 cases of choroid plexus papilloma (CPP) and 19 of ependymoma, using the peroxidase antiperoxidase technique. Among the 11 cases of CPP, all 11 were positive for CKER, EMA, and TTR, 10 for S-100 protein, and five for GFAP. Most of the GFAP-positive papilloma cells were simultaneously positive for CKER. However, these GFAP-positive cells were negative for TTR. Among the 19 cases of ependymoma, 16 were positive for GFAP, 17 for S-100 protein, three for CKER, eight for EMA, but none for TTR. Some GFAP-positive cells were also stained for CKER. However, TTR was not found in any of the ependymal cells. These findings suggested that CPP cells which show ependymal or glial differentiation lost the ability to synthesize TTR which is known to be synthesized in the epithelial cells of the choroid plexus. The more GFAP-positive cells present in a CPP, fewer TTR-positive cells are present. Though CPPs are usually easily distinguishable from ependymomas, occasional doubt arises concerning the differential diagnosis between CPP and papillary ependymoma. TTR can be a very useful diagnostic marker of CPP.