Immunohistochemical Staining in Malignant Mesotheliomas

Abstract

The immunoreactivity of five antibodies was evaluated on six routinely processed mesotheliomas to evaluate their ability to distinguish mesothelioma from metastatic adenocarcinoma. The diagnosis in all cases was confirmed by electron microscopic examination and histochemical stains for neutral mucin (periodic acid-Schiff-diastase) and acid mucin (alcian blue with and without hyaluronidase). AE1, a monoclonal antikeratin antibody that stains most carcinomas, reacted with all six cases of mesothelioma. HMFG-2 and anti-epithelial membrane antigen (antibodies reactive with human milk fat globule proteins), two other closely related antibodies reactive with most carcinomas, also reacted with all of the mesotheliomas in the authors' series. A polyclonal antibody to carcinoembryonic antigen (anti-CEA) did not stain any of the mesotheliomas in their series. Anti-Leu-M1 did not react with the mesotheliomas. The authors conclude that none of these antibodies, when used alone on routinely fixed paraffin-embedded material, is both sensitive and specific in the distinction of mesothelioma from adenocarcinoma. However, immunoperoxidase studies using anti-CEA and anti-Leu-M1 may occasionally be helpful when used in conjunction with other histochemical stains and electron microscopic examination in distinguishing mesothelioma from metastatic adenocarcinoma.