PURPOSE: Pleural effusions are frequently the presenting symptom of neoplastic disease. However, the diagnosis is often difficult, and specialised techniques, such as molecular tests with specific markers, are required. The aim of the present study was to investigate the diagnostic significance of RT-PCR detection of human mammaglobin (hMAM) mRNA in pleural effusions (PE) of unknown origin.
METHODS: PE fluid was obtained from patients diagnosed between February 2002 and December 2007. All specimens were analysed by cytology and, when necessary, by histology of pleural biopsy taken during medical thoracoscopy. A definitive diagnosis was obtained for all patients. We studied 413 PE, 228 from patients with cancers (32 breast cancers, 77 lung cancers, 80 mesotheliomas, 39 others) and 185 from benign diseases. All the samples were subjected to nested RT-PCR for hMAM. Comparative analysis by Fisher exact test of hMAM expression between malignant PE Vs benign PE and diagnostic performances parameters were assessed. The results of hMAM detection were also compared with conventional cytology.
RESULTS: hMAM was expressed in 114 out of 413 (27.6%) total PE; in 104/228 (45.6%) neoplastic PE (27 breast cancers, 34 lung cancers, 29 mesotheliomas, 14 others) and in 10/185 (5.4%) benign PE (Fisher exact test p<0.0001). The hMAM sensivity for neoplastic PE was 45.6% and the specificity was 94.6%; accuracy, positive predictive value and negative predictive value were 67.6%, 91.2% and 58.5%, respectively. The cytology in neoplastic PE was positive in 122 patients.Comparative analysis of hMAM RT-PCR and cytology in the specimens from neoplastic PE showed that 70 samples (30.7%) were positive by both PCR and cytology, 34 (14.9%) were positive only by PCR, 52 (22.8%) were positive only by cytology and 72 (31.6%) were negative by both tests.
CONCLUSION: RT-PCR for hMAM has the potential to add clinically significant information to conventional cytology in the work-up of patients with a PE of unknown origin.
CLINICAL IMPLICATIONS: Thoracoscopy should be always performed in patients with an hMAM positive pleural effusion of unknown origin.
DISCLOSURE: Pier Aldo Canessa, No Financial Disclosure Information; No Product/Research Disclosure Information