Assessment of RT-PCR detection of human mammaglobin for the diagnosis of breast cancer derived pleural effusions

The present study investigates the diagnostic significance of human mammaglobin (hMAM) mRNA expression in pleural effusions (PE) from breast cancer (BC) patients. Two hundred and fifty PE samples, including 32 from patients who had diagnosis of BC, 116 from patients with other cancers, and 102 from patients with benign diseases, were subjected to nested reverse-transcription polymerase chain reaction (RT-PCR) for hMAM, and the results were compared with conventional cytology. hMAM was found expressed in 76/250 (30.4%) total PE and in 23/28 (sensitivity of 82.1%) of the PE subgroup owing to metastasis from BC. The specificity for hMAM detection method was 75.7%, whereas accuracy, positive predictive value, and negative predictive value were 76.4%, 30.3%, and 97.1%, respectively. hMAM was also detected in 46/116 (39.6%) PE specimens from other types of cancer and in 7/102 (6.8%) from benign diseases. Comparative analysis of RT-PCR and cytology showed that 14 PE samples from metastatic BC (50%) were positive by both PCR and cytology, 9 (32.1%) were positive only by PCR and 5 (17.9%) were negative by both tests, whereas no cases were found of positive cytology with negative PCR. RT-PCR increased sensitivity of BC effusion detection to 32.1% (McNemar test, P=0.004). We demonstrated that RT-PCR for hMAM test was more sensitive than cytomorphology suggesting that, although hMAM is not BC specific, it may be useful in adjunct to cytology for the routine screening of malignant BC effusions.