Correlation between pleural fluid cytology and magnitude of pleural invasion in patients with malignant pleural mesothelioma

Abstract

Malignant pleural mesothelioma (MPM) is an aggressive tumor commonly triggered by exposure to asbestos, and commonly presented with unilateral pleural effusion. Pleural fluid cytological assessment is often the first diagnostic step that leads to a confirmed diagnosis in a relatively small percentage of cases. Medical thoracoscopy is considered as the procedure of choice to achieve a definite diagnosis and evaluate the extent of the disease. The aim of this study was to assess the correlation between pleural fluid cytological yield and the invasion of different pleural surfaces detected by means of medical thoracoscopy. In this retrospective study, the medical records of all patients with confirmed MPM who underwent medical thoracoscopy at the Chest Department of Ain Shams University Hospitals from May 2012 to May 2016 were analyzed. Patients were included only if the results of pleural fluid cytology were available, as well as the detailed reports of medical thoracoscopy. We included 85 patients with MPM in this study, 71 male and 14 female, with a mean age of 61.56±8.75 years. Types of MPM were epitheliod type (64.7%), biphasic type (23.5%), and sarcomatoid type (11.8%). Positive pleural fluid cytology was found in 24 patients (28.2%). Medical thoracoscopy demonstrated parietal pleural invasion in all patients (100%) and visceral pleural invasion in 26 patients (30.5%). Visceral pleural invasion was found in 83.3% of patients with positive pleural fluid cytology. Our results demonstrated that the presence of visceral pleural invasion could predict a positive pleural fluid cytology with a sensitivity of 79.17%, specificity of 88.52%, positive predictive value of 73.08%, and negative predictive value of 91.83. The pattern of visceral pleural invasion had no impact on the results of pleural fluid cytology (P>0.05). The results of our study showed that the overall diagnostic yield of pleural fluid cytology in MPM is 28.2%. Positive pleural fluid cytology results were found to be significantly higher in cases with visceral pleural invasion, and, as visceral pleural invasion indicates a more advanced disease, the positive pleural fluid cytological results may be considered an indicator for advanced MPM.