The presence of blood and/or air in the pleural cavity is thought to be the leading cause of eosinophilic pleural effusions (EPE). The frequency of malignancy among EPE is controversial. Moreover, since malignant pleural effusions (MPE) are frequently bloody, it is not clear whether the reason of pleural fluid eosinophilia in MPE is the presence of blood. In this study we hypothesized that malignancy is a common cause of EPE and that pleural fluid eosinophilia in MPE is frequently due to the presence of blood.
A data-base containing data from 1195 pleural effusions was searched for EPE, defined as the effusions that contained more than 10% eosinophils at the first thoracentesis, and MPE (again only at first thoracenesis).
One hundred and seventy-two EPE were found. The most common etiology was heart surgery (68%), followed by malignancy (8.7%), parapneumonic (4.6%), heart failure (4.6%) and other diseases (4.1%). No etiology was found in 10% of the cases. We also identified 170 MPE; 13 of them were bloody, defined as those with at least 100,000 red blood cells/mm3. Three of the 13 bloody MPE (23%), and 12 of the 157 (7.6%) non-bloody MPE were EPE (Fisher’s exact test: p=0.093).
Malignancy was the second most common cause of EPE. Although bloody MPE tended to be eosinophilic more frequently than the non-bloody MPE, 80% of the eosinophilic MPE were not bloody, suggesting that factors other than blood contribute to pleural fluid eosinophil accumulation in MPE.
The presence of pleural fluid eosinophilia in a non-bloody pleural effusion does not rule out the diagnosis of malignancy.
I.T. Kalomenidis, None.