Immunocytochemistry and ELISA Quantitation of Mucin for Diagnosis of Malignant Pleural Effusions

One hundred and thirty-five pleural effusions with definite etiology were analyzed by mucin-specific monoclonal antibody (17Q2)-derived enzyme-linked immunosorbent assay (ELISA). Twenty-four effusions were transudate, 45 were nonmalignant exudate, and 66 were malignant. Among the 66 malignant effusions, 52 were adenocarcinoma, and 14 were malignancies other than adenocarcinoma. Purified mucous glycoproteins from sputa of normal subjects were used as ELISA standard. Our results showed that the mean mucin concentration in malignant pleural effusions were significantly higher than that of benign exudates (8.41 ± 13.48 ng/ml versus 1.09 ± 0.82 ng/ml, p < 0.01). Mucin concentration in malignant pleural effusions caused by adenocarcinoma was also significantly higher than in nonadenocarcinoma effusions (9.96 ± 14.81 ng/ml versus 2.66 ± 1.74 ng/ml, p < 0.01). With the use of mean ±2 SD of mucin concentration in benign exudates as a cut-off value (2.73 ng/ml), the sensitivity of this assay for diagnosis of malignant effusions was 66.7%, specificity was 97.1%, and accuracy was 82.2%. High levels of mucin concentration were more specifically associated with adenocarcinoma. When the mucin concentration in pleural effusions was greater than 5 ng/ml, 93.1% (27/29) of patients were adenocarcinoma. If the mucin concentration was greater than 10 ng/ml, 100% (14/14) of patients were adenocarcinoma. Immunofluorescent staining by mucin-specific monoclonal antibody 17Q2 were also carried out in diastase-treated cell preparations obtained from 22 patients with malignant pleural effusions and 16 benign exudates. Nine of 14 adenocarcinomas (64.2%) were reactive with monoclonal antibody 17Q2, while none of the benign exudates, squamous cell carcinomas, and mesotheliomas were stained. In this preliminary study, we conclude that ELISA quantitation of mucin concentration and immunocytochemistry by mucin-specific monoclonal antibody may be potentially useful for diagnosis of malignant pleural effusions.