Pleural lavage cytology: where do we stand?

Although a malignant pleural effusion is considered a manifestation of an advanced stage disease not amenable to curative resection in patients with non-small cell lung cancer, the same is not true in the case of the presence of malignant cells in the pleural cavity without an accompanying effusion, discovered incidentally during the operation with pleural lavage cytology (PLC). PLC is a diagnostic technique used to detect tumor cells and translate this finding to a prognostic index. Various reports have attempted to utilize the results of PLC and draw inferences regarding the origins of malignant cells in the pleural cavity, the association of these results with various disease characteristics and, most importantly, their impact on disease recurrence and survival. However, due to non-consistent techniques and protocols used to acquire the samples for cytological evaluation and assess their significance, results are inhomogeneous. Nevertheless, the entrance of malignant cells in the pleural cavity follows the rules posed by the natural disease process when discovered before pulmonary resection takes place, while surgical manipulations certainly play an important role in the case malignant cells are checked over after pulmonary resection. In addition, although the prognostic significance of a positive PLC result is indisputable and significantly decreases long-term survival in the majority of studies, this factor has not yet been incorporated into the TNM staging system. Lastly, some authors have advocated the use of some form of adjuvant treatment for those patients found with positive PLC results, based on the assumption that a curative resection followed by multiple pleural washings will not remove the entirety of the population of malignant cells present in the pleural space.