Evaluation of epithelial and keratin markers in glioblastoma multiforme - An immunohistochemical study

Objective.-Poorly differentiated metastatic carcinoma may be difficult to d istinguish histologically from high-grade astrocytic malignant neoplasms, p articularly on small open or stereotactic biopsy specimens. Previous author s have reported that a subset of glioblastoma multiforme (GBM) variably sta ins with cytokeratin immunomarkers. The authors examined a panel of epithel ial and keratin antibodies by paraffin immunohistochemistry to evaluate the immunophenotype of CBM for these markers and to determine what combination of immunostains would be optimal in distinguishing GBM from metastatic car cinoma. Methods.-Twenty-three patients with GEM (age range, 19-86 years; mean, 63.4 years; 14 men and 9 women) and 22 patients with metastatic carcinoma (age range, 26-77 years; mean, 58.1 years; 7 men and 15 women) to the brain were studied with a panel of immunostains, including glial fibrillary acid prot ein (GFAP), Ber-EP4, antikeratin monoclonal antibodies AE1/3, and antibodie s to CAM 5.2 and cytokeratins 7 (CK7) and 20 (CK20). Sites of origin for th e metastatic tumors included lung (n = 11), breast (n = 5), endometrium (n = 1), prostate (n = 1), colon (n = 1), presumed kidney (n = 1), and unknown (n = 2). Results.-All GBMs stained positive for GFAP (100%), and all but 1 (95.7%) s tained positive for cytokeratins AE1/3. Only rare focal immunoreactivity wa s observed in a single case of GEM with CAM 5.2 (4.3%), CK7 (4.3%), and CK2 0 (4.3%). Immunoreactivity with Ber-EP4 was not observed in any of the GBMs (0.0%). All cases of metastatic carcinoma stained positive with cytokerati ns AE1/3 (100%) and CAM 5.2 (100%). Variable staining was observed in carci nomas with CK7 (17 of 22, 77.3%), Ber-EP4 (11 of 22, 50.0%), and CK20 (9 of 22, 40.9%). Three metastatic carcinomas showed rare GFAP-positive staining cells (13.6%). Conclusions.-Based on the aforementioned results, a combination of immunost ains, including GFAP and cytokeratin CAM5.2, may be the most useful in diff erentiating poorly differentiated metastatic carcinoma from GBM. A signific ant number of GBMs stain with some cytokeratin markers, in particular cytok eratins AE1/3. Because of the poor specificity of cytokeratins AE1/3 in dis tinguishing metastatic carcinoma from GBM, it should not be used to differe ntiate the 2 entities.