Immunohistochemical properties of malignant mesothelioma cells in histologic and cytologic specimens

Although there is general agreement that immunohistochemical methods can aid in the pathologic diagnosis of malignant mesothelioma, some studies have produced conflicting results. To obtain comparable and reproducible results, unequivocal malignant mesotheliomas were studied with the biotin-streptavidin-peroxidase complex method in 14 formalin-fixed, paraffin-embedded tissue specimens, 5 ethanol-fixed smear slides and 3 cold acetone-fixed smear slides. The expression of CA-125, epithelial membrane antigen (EMA) and vimentin by malignant epithelial mesothelioma cells was hindered by their poor preservation in formalin fixative. Cytologic specimens fixed in cold acetone were the best type for immunohistochemistry. The majority of malignant epithelial mesothelioma cells in the smear slides fixed in cold acetone were positive for CA-125, EMA, low-molecular-weight cytokeratin and vimentin, but none of them were positive for carcinoembryonic antigen, CA-19-9, epithelial antigen, high-molecular-weight cytokeratin or Leu-M1.