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Diagnostic utility of E-cadherin (E-CD) and cytokeratin (CK) subtype profiling in effu-sion cytology was investigated, employing immunocytochemistry on cellblock sec-tions available from 211 metastatic carcinomas (MC), 6 mesotheliomas and 73 reac-tive mesothelial hyperplasias (MH). E-CD and monoclonal carcinoembryonic anti-gen (mCEA) stained 85% (120/141) and 65% (138/211) of MC, respectively. E-CD staining of MC was frequently heterogeneous (76/120) and absent in all anaplastic carcinomas (0/2). E-CD stained none (0/57) of MH while mCEA and epithelial mem-brane antigen (EMA) stained 12% (9/73) and 32% (16/32) of MH, respectively. Of 6 mesotheliomas, E-CD focally stained in 2 while mCEA stained none and EMA stained all. CK20 and CK17 stained none of MH or mesotheliomas. CK20 stained 15% of MC and CK 17 stained 22% of MC. CK5/6 and high molecular weight CK stained all mesotheliomas, 56% and 88% of MH, 26% and 39% of MC, respectively. MC showed predominant CK7+/20-expression, with the exceptions of MC from muci-nous type of colon/rectum and ovary showing predominant CK20 positive. E-CD may be a useful positive marker for MC in effusion cytology, although it may focally stain in some mesotheliomas. Any positive staining for CK20 of MC suggests MC from the gastrointestinal tract or ovary among others.
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