Recognition of malignant effusion relies heavily on cytologic examination despite the difficulty of distinguishing atypical mesothelial
hyperplasia from metastatic
carcinoma. The combination of CEA, EMA,
vimentin,
keratin, high-molecular-weight
cytokeratin (
HMWK), low-molecular-weight
cytokeratin (
LMWK), and
Alcian blue was tested in 51 cytologic specimens of pleural, peritoneal, and
pericardial effusions. These showed metastatic
carcinoma in 38 cases (ovary, 14; lung, 8; breast, 7; GI, 4; endometrium, 4; bladder, 1) and mesothelial processes in 13 (
hyperplasia, 9;
mesothelioma, 4). Strong positivity for EMA (92%), CEA (90%), and
Alcian blue (71%) was noted in metastatic
carcinoma but not in the mesothelial processes.
Keratin was positive in all cases of
mesothelioma but occurred also in mesothelial
hyperplasias (44%) and metastatic
carcinomas (47%). In mesothelial cells,
HMWK was consistently stronger than
LMWK, whereas in
adenocarcinoma the reverse was true. There was no difference in the degree or distribution of positivity of any of the markers among the various primary sites of the
neoplasms. Our findings are consistent with the view that immunocytochemistry with a battery of
antibodies is useful in the recognition of malignant effusions but cannot, as yet, determine the site of origin of metastatic
neoplasms.