DISTINGUISHING MALIGNANT MESOTHELIOMA FROM PULMONARY ADENOCARCINOMA - AN IMMUNOHISTOCHEMICAL APPROACH USING A PANEL OF MONOCLONAL-ANTIBODIES

A panel of six monoclonal antibodies (MAbs) was employed to evaluate antigen expression in pulmonary adenocarcinomas and mesotheliomas. Monoclonal anti‐human milk fat globulin (HMFG‐2), anti‐carcinoembryonic antigen (NP‐2), antiepithelial membrane antigen (EMA), anticytokeratin (PKK‐ l), anti‐tumor‐associated antigen 72 (B72.3), and anti‐human myelomonocytic antigen (Leu M‐1) antibodies were used to localize their respective antigens in formalin‐fixed, paraffin‐embedded tumors by using the avidin‐biotin‐complex immunoperoxidase technique. In all, 28 mesotheliomas obtained from Ohio State University Anatomic Pathology files and from a Southwest Oncology Group (SWOG) protocol were compared to 22 pulmonary adenocarcinomas by using this MAb panel. None of the mesotheliomas demonstrated positive staining with MAbs NP‐2 (anti‐CEA) or Leu M‐1. However, 95% (21/22) of adeno‐ carcinomas stained with one of these two antibodies. Although neither of these two MAbs stained all adenocarcinomas, each antibody demonstrated positive immunostaining in more than 90% of the adenocarcinomas studied. Therefore, MABs NP‐2 and Leu M‐1 are, individually, quite useful for distinguishing mesothelioma from adenocarcinoma. However, in our study, no single MAb could be used to distinguish these two tumor types in every case. MAb B72.3 stained 91% (20/21) adenocarcinomas but also stained 7% (2/28) of mesotheliomas. MAb HMFG‐2 reacted positively with 95% of adenocarcinomas, but also stained 39% of the mesotheliomas, usually in a membranous pattern. MAbs EMA and PKK‐1 were not found useful in distinguishing mesothelioma from adenocarci‐noma. We conclude that MAbs Leu M‐1 and NP‐2 were both useful in distinguishing mesothelioma from pulmonary adenocarcinoma in that positive staining was demonstrated in adenocarcinomas and not mesothe‐liomas. Copyright © 1990 Wiley‐Liss, Inc., A Wiley Company