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Communications to the Editor |

Should a Cytologic Study Be Ordered in Transudative Pleural Effusions? FREE TO VIEW

José Manuel Porcel, MD; Mar Alvarez, MD; Antonieta Salud, MD; Manuel Vives, MD
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University Hospital Arnau de Vilanova Lleida, Spain Clinica Recoletas Albacete, Spain

Correspondence to: José Manuel Porcel, MD, Professor and Chairman, Department of Medicine, University of Lleida, Av Alcalde Rovira Roure 80, University Hospital Arnau de Vilanova, 25198 Lleida, Spain; e-mail: jporcelp@medynet.com



Chest. 1999;116(6):1836-1837. doi:10.1378/chest.116.6.1836
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To the Editor:

The criteria of Light1are widely used in clinical practice as a first step in determining whether a pleural effusion is an exudate or a transudate. Traditionally, it has been thought that no further diagnostic studies are necessary if the effusion is a transudate. However, at many institutions all undiagnosed pleural fluids are studied cytologically, probably because there is still concern about misleading malignant disease. The original study of Light and colleagues2involved 43 malignant effusions, 1 of which was classified as a transudate. This patient with breast cancer was in congestive heart failure, and the effusion completely resolved with diuretics. Few studies have attempted to determine the distribution of transudates and exudates in pathologically proved malignant pleural effusions,37 and opposite recommendations regarding the necessity for cytologic evaluation in transudative pleural effusions are evoked by the authors of those studies. Whereas some authors favor the routine cytologic evaluation of all pleural effusions even if they are transudates,57 others do not recommend it at all when the effusion is transudative.3 We wish to report the results of our study to justify our intermediate position.

We retrospectively reviewed the medical records of 120 consecutive patients with cytologically proved malignant pleural effusions who had been seen at our institution during the previous 3 years. Twenty patients were excluded because of incomplete data on pleural fluid analysis. Of the 100 patients enrolled in the study, there were 58 female and 42 male patients, who had a mean age of 66 years (range, 28 to 91 years). The distribution of malignant tumors was as follows: lung cancer (n = 37); breast cancer (n = 35); ovarian carcinoma (n = 9); unknown primary tumor (n = 5); mesothelioma (n = 3); and miscellaneous tumors (n = 11). Two patients met the criteria of Light for a transudate. The first was a 61-year-old man with lung cancer producing atelectasis, a known cause of transudative pleural effusion. The second was a 75-year-old man who presented with a lung mass that proved to be malignant, metastases to the brain and liver, and a bilateral pleural effusion. Because of sufficient clinical clues, the diagnosis of an underlying malignancy would not be misleading despite the presence of pleural fluid with transudative characteristics. However, premature death precluded the evaluation of potential causes for this transudate.

As summarized in Table 1 , malignant pleural effusions may be transudates in 1 to 10% of patients. The conclusions of several studies can be criticized because they do not report whether there were other explanations for the condition of their patients with transudates cytologically proved to be malignant.57 In the largest series from Ashchi et al4 8 patients with transudative malignant pleural effusions among 171 patients were identified, and all except 1 had a satisfactory explanation for the transudate.

To conclude, we suggest an intuitive approach, ie, performing a cytologic study in transudates, only when clinical judgment dictates that the pleural effusion is not related to the few conditions associated with transudates.

Table Graphic Jump Location
Table 1. Distribution of Transudative and Exudative Malignant Pleural Effusions Using the Criteria of Light*
* 

CI = confidence interval.

References

Light, RW (1995)Pleural diseases 3rd ed. ,36-74 Williams & Wilkins. Baltimore, MD:
 
Light, RW, MacGregor, IM, Luchsinger, PC, et al Pleural effusions: the diagnostic separation of transudates and exudates.Ann Intern Med1972;77,507-13. [PubMed]
 
Assi, Z, Caruso, JL, Herndon, J, et al Cytologically proved malignant pleural effusions: distribution of transudates and exudates.Chest1998;113,1302-1304. [PubMed] [CrossRef]
 
Ashchi, M, Golish, J, Eng, P, et al Transudative malignant pleural effusions: prevalence and mechanisms.South Med J1998;91,23-26. [PubMed]
 
Moltyaner, Y, Miletin, M, Grossman, RF Transudative pleural effusions: false reassurance against malignancy [abstract]? Chest. 1997;;112(suppl) ,.:13S
 
Castro, DJ, Nuevo, GD, Pérez-Rodriguez, E Cytologically proved malignant pleural effusions [letter]. Chest. 1998;;114 ,.:1798
 
Foresti, V, Scolari, N, Villa, A Positivity of pleural fluid cytologic examination in transudative pleural effusions [letter].Chest1998;114,1798-1799
 

Figures

Tables

Table Graphic Jump Location
Table 1. Distribution of Transudative and Exudative Malignant Pleural Effusions Using the Criteria of Light*
* 

CI = confidence interval.

References

Light, RW (1995)Pleural diseases 3rd ed. ,36-74 Williams & Wilkins. Baltimore, MD:
 
Light, RW, MacGregor, IM, Luchsinger, PC, et al Pleural effusions: the diagnostic separation of transudates and exudates.Ann Intern Med1972;77,507-13. [PubMed]
 
Assi, Z, Caruso, JL, Herndon, J, et al Cytologically proved malignant pleural effusions: distribution of transudates and exudates.Chest1998;113,1302-1304. [PubMed] [CrossRef]
 
Ashchi, M, Golish, J, Eng, P, et al Transudative malignant pleural effusions: prevalence and mechanisms.South Med J1998;91,23-26. [PubMed]
 
Moltyaner, Y, Miletin, M, Grossman, RF Transudative pleural effusions: false reassurance against malignancy [abstract]? Chest. 1997;;112(suppl) ,.:13S
 
Castro, DJ, Nuevo, GD, Pérez-Rodriguez, E Cytologically proved malignant pleural effusions [letter]. Chest. 1998;;114 ,.:1798
 
Foresti, V, Scolari, N, Villa, A Positivity of pleural fluid cytologic examination in transudative pleural effusions [letter].Chest1998;114,1798-1799
 
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