Abstract
Malignant pleural effusion (MPE) is a common feature in patients with advanced or metastatic malignancies. While significant progress has been made in understanding the biology of pleural effusions, further research is needed to uncover the subsequent behavior of tumor cells following their invasion into the pleural space. This report utilizes flow cytometry to analyze DNA content abnormalities (aneuploidy) and cell cycle status, shedding light on the tumor cell populations present in MPE samples from a patient with lung adenocarcinoma during treatment. The findings suggest that under selective pressure, certain tumor cell subpopulations within the pleural effusion were suppressed, while therapy-resistant subpopulations emerged, driving disease progression. MPE serves as a valuable model for studying tumor heterogeneity and clonal dynamics in real time, offering insights that may inform diagnosis, prognosis, and therapeutic strategies.