Only recently have immunohistochemical markers been recognized that are commonly expressed in epithelial
mesotheliomas but not in
adenocarcinomas. Among these,
calretinin generated a great deal of interest, but the number of studies evaluating the practical use of
calretinin immunostaining in the diagnosis of
mesothelioma is limited, and the study results are controversial. To evaluate whether
calretinin immunostaining can assist in distinguishing between epithelial pleural
mesothelioma and
lung adenocarcinoma and other
carcinomas metastatic to the pleura, 38 pulmonary
adenocarcinomas, 117 nonpulmonary
adenocarcinomas, 28
squamous cell carcinomas of the lung, 8 large-cell
undifferentiated carcinomas of the lung, and 9
transitional cell carcinomas metastatic to the lung were studied. Reactivity was observed in all of the 38
mesotheliomas, whereas only 3 of the 38 pulmonary
adenocarcinomas and 11 of the 117 nonpulmonary
adenocarcinomas (5/38 ovarian, 2/15 endometrial, 2/23 breast, 2/16 colonic, 0/8 kidney, 0/8 prostatic, 0/6 thyroid, and 0/3 pancreatic) exhibited weak or focal staining. Eleven of the 28
squamous carcinomas of the lung were also positive. No reactivity was observed in any of the large cell
undifferentiated carcinomas of the lung or in the
transitional cell carcinomas. It is concluded that
calretinin immunostaining is not only helpful in discriminating epithelial pleural
mesotheliomas from pulmonary
adenocarcinomas but that it can also assist in distinguishing epithelial
mesotheliomas from nonpulmonary
adenocarcinomas metastatic to the pleura.