University Hospital Arnau de Vilanova
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: email@example.com
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,3–7 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,5–7
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.5–7 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.
CI = confidence interval.
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