Visceral pleura invasion and pleural lavage tumor cytology by lung cancer: a prospective appraisal

Background Despite an early-stage diagnosis, lung cancer presenting with visceral pleura invasion (VPI) or malignant pleural lavage cytology (PLC) has a poor prognosis. The purpose of this study was to correlate VPI to malignant PLC. Methods One hundred forty-three consecutive patients scheduled for surgical lung resection having undergone preresectional pleural lavage cytology were reviewed. There were 121 malignant and 22 nonmalignant lesions. All cases were studied by pathology, histology, previous transthoracic puncture, VPI, and presence of pleural lymphatic involvement. Results PLC was positive (n = 13) or suspected (n = 5) for malignant cells in, respectively, 10.7% and 4.1% of patients with lung cancer. There was no positive PLC in cases of nonmalignant disease. PLC was positive only in pT2 tumors and almost always when the tumor was exposed on the pleural surface, thus possibly exfoliating within the pleural space (12/17 patients, 70.6%; p< 0.01). Positive PLC was obtained whatever the histology but did not appear related to previous transthoracic puncture or involvement of pleural lymphatics by tumor cells. Conclusions VPI and positive PLC are linked, and the appearance of tumor cells within the pleural cavity can be explained by tumor desquamation. The role that visceral pleura involvement and parietal pleura reabsorption play in lung cancer is of paramount importance and deserves further research. A better understanding of their relationship could have major implications in the therapeutic management of non–small cell lung cancer.