The immunophenotype of ependymomas.
The morphologic distinction of ependymomas with epithelial cytology from metastatic carcinoma may pose a significant problem in differential diagnosis. The known presence of keratin in glioma cells further complicates the issue. Using the labeled streptavidin-biotin method with automated staining, we studied epithelial and glial marker expression in 52 ependymomas of varying type and grade, including 20 epithelial-appearing, 14 glial-appearing, eight mixed pattern, and 10 myxopapillary tumors; 38 were low grade and 14 anaplastic. All tumors were immunoreactive for glial fibrillary acidic protein (GFAP), and S-100 protein. Diffuse staining for GFAP was noted in glial-appearing ependymomas featuring perivascular pseudorosettes. Diffuse immunostaining for S-100 protein was seen in cellular lesions exhibiting epithelial-like features. Staining was more diffuse for GFAP than S-100 protein in anaplastic ependymomas. Keratin (AE1/AE3) reactivity was seen in 98% of cases, the pattern being similar to that of GFAP. The frequency of staining for other keratins varied: wide-spectrum keratin (35%), cytokeratin (CK)7 (20%), CAM 5.2 (19%), CK903 (14%), and CK20 (8%); as a rule, it was scant and limited to occasional cells and processes. epithelial membrane antigen ( EMA) staining was seen in 36% of all cases and in 67% of epithelial-appearing tumors wherein it often high-lighted microlumina. Aside from AE1/AE3 staining and very infrequent wide-spectrum keratin and EMA reactivity, expression of epithelial markers was not seen in anaplastic ependymomas. No carcinoembryonic antigen ( CEA) positivity was noted in any case. Collagen IV reactivity was limited to tumor cell-stroma interfaces. Although variable, S-100 protein and GFAP staining is seen in all ependymomas, particularly in true and perivascular pseudorosettes. Widespread reactivity for keratin AE1/AE3 corresponds closely to the pattern of GFAP staining. Significant staining for other keratins or for CEA is inconsistent with a diagnosis of ependymoma. EMA reactivity is largely limited to luminal staining of rosettes and tubules.[1]References
- The immunophenotype of ependymomas. Vege, K.D., Giannini, C., Scheithauer, B.W. Appl. Immunohistochem. Mol. Morphol. (2000) [Pubmed]
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