Eosinophilic pleural effusion (EPE) is defined as a pleural fluid with an eosinophilic count exceeding 10% and currently considered to be mainly caused by malignancy. However, the incidence, etiology and prognostic significance of malignant eosinophilic pleural effusion (MEPE) have not been studied extensively yet. Thus, the objective of this review was to summarize medical studies regarding MEPE to 2020 throughout an extensive search of PubMed. Overall, MEPE was a disease associated with multiplecytokines-mediated immunity and varied from 4% to 92% of patients who had EPE. The discrepancy of the MEPE prevalence among studies could be explained by the development of diagnostic technology, disparity of study population, or various disease spectrum over time. Data summarized in this review demonstrated that the incidence of malignancy was lower in EPEs than in non-EPEs (29.7% vs. 32.9%). Additionally, MEPE could be a manifestation of a great variety of tumor subtypes, among which lung cancer was the most common cause and accounted for more than 34% of cases. The second common causes were non-Hodgkin lymphoma and metastatic cancers with unknown primary site which were observed in around 5% of cases, respectively. The presence of eosinophils in the pleural effusion may be associated with a positive prognosis of MEPE. Besides, the prognosis of MEPE may be related to the percentage of eosinophils in the pleural fluid. More extensive studies, however, are warranted to validate these findings.
Keywords: Malignant eosinophilic pleural effusion (MEPE); etiology; incidence; prognosis.