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Pleural Effusion with Negative Cytology

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OncoLink Team
The Abramson Cancer Center of the University of Pennsylvania
Last Modified: May 7, 2013

Question

My mom was treated for stage IIIA lung cancer (non-small cell lung cancer). She had chemotherapy combined with radiation therapy, finished treatment in March, and was declared in remission in May. In August, she had a pleural effusion, but a CT scan and PET scan showed nothing. They drained the fluid in her lungs and did not find cancer. She is currently having heart tests to determine the reason for the effusion, but the cardiologist does not think it is heart related. He said it is possible to have underlying cancer recurrence without having it appear in the fluid (they checked all of it). She's having tests next week to see if it has returned. Can you tell me if he is correct?

Answer

Anil Vachani, MD, Pulmonologist at Penn Medicine, responds:

In general, pleural effusions due to malignancy are exudative in nature; this means that the total protein and LDH levels in the fluid are high. Pleural effusions secondary to heart failure are generally transudative (low total protein and LDH). To confirm that an effusion is malignant generally requires the documentation of malignant cells by cytological examination of the fluid. However, in approximately 50% of effusions caused by cancer, no malignant cells are identified when the pleural fluid is viewed under a microscope. The standard is to perform 3 repeated thoracenteses, which when combined, raise the yield of detecting malignant cells to about 80%. If the results of the pleural fluid are still negative after repeated thoracentesis and malignancy is still being considered, patients often require a biopsy of the lining of the lung.