Cytologically proved malignant pleural effusions: distribution of transudates and exudates

Chest. 1998 May;113(5):1302-4. doi: 10.1378/chest.113.5.1302.


Purpose: This study attempts to determine the distribution of transudates vs exudates in pathologically proved malignant pleural effusions and the necessity for cytologic studies in patients with a transudative effusion.

Materials and methods: A retrospective review of all cytologically positive malignant pleural effusions was performed at Duke University Medical Center over an 18-month period. All effusions were characterized as a transudate or an exudate based on standard criteria, including lactate dehydrogenase and protein values.

Results: Ninety-eight patients with a mean age of 62 years were identified as having a cytologically positive malignant pleural effusion and blood chemistry values available to distinguish an exudate from transudate. Ninety-seven patients (99%, 95% confidence interval; 0.94 to 0.99) had criteria for an exudative effusion. One patient (1%) with diffuse metastatic lung cancer had a borderline transudate and was in congestive heart failure at the time of thoracentesis.

Conclusions: Cytologically positive pleural effusions for malignancy are almost always exudates. Cytologic evaluation for malignant cells of a transudative pleural effusion is not recommended.

MeSH terms

  • Diagnosis, Differential
  • Exudates and Transudates / cytology
  • Female
  • Humans
  • Male
  • Middle Aged
  • Pleural Effusion, Malignant / diagnosis
  • Pleural Effusion, Malignant / epidemiology
  • Pleural Effusion, Malignant / pathology*
  • Retrospective Studies