Eosinophilia in Pleural Effusions: a Speculative Negative Predictor for Malignancy.

Area of Science:

• Pulmonology
• Cytopathology
• Oncology

Background:

• Eosinophilic pleural effusion (EPE) is defined by >10% eosinophils in pleural fluid cytology.
• Malignancy is increasingly recognized as a primary cause of EPE.
• This study investigates the prevalence, causes, and relationship between EPE and malignancy.

Purpose of the Study:

• To determine the prevalence and etiology of EPE.
• To explore the association between EPE and malignancy.
• To identify potential diagnostic markers for differentiating EPE causes.

Main Methods:

• Retrospective analysis of 6,801 pleural cytology requests from 3,942 patients (2008-2013).
• Comparison of pleural fluid differential counts with clinical data and diagnoses.
• Evaluation of the relationship between pleural fluid eosinophil percentage and malignancy.

Main Results:

• EPE was found in 2.9% of patients (115 cases).
• Malignancy was the leading cause (33.0%), followed by parapneumonic effusions (27.8%) and tuberculosis pleuritis (13.9%).
• An inverse correlation was observed between pleural eosinophil percentage and malignancy; a 15% cut-off showed 65.8% sensitivity and 67.5% specificity for distinguishing malignancy.

Conclusions:

• Pleural fluid eosinophilia can be a negative predictor for malignancy, despite cancer being a common cause of EPE.
• An inverse relationship exists between pleural eosinophil percentage and the likelihood of malignancy in EPE patients.
• A 15% pleural fluid eosinophil threshold aids in differentiating malignant from benign causes of EPE.