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  • Occur in pleural, pericardial, and peritoneal spaces.

  • Caused by direct neoplastic involvement of serous surface or obstruction of lymphatic drainage.

  • Half of undiagnosed effusions in patients not known to have cancer are malignant.


The development of an effusion in the pleural, pericardial, or peritoneal space may be the initial finding in a patient with cancer, or an effusion may appear during the course of disease progression. Direct involvement of the serous surface with tumor is the most frequent initiating cause of the accumulation of fluid. The most common malignancies causing pleural and pericardial effusions are lung and breast cancers; the most common malignancies associated with malignant ascites are ovarian, colorectal, stomach, and pancreatic cancers.


A. Symptoms and Signs

Patients with pleural and pericardial effusions complain of shortness of breath and orthopnea. Patients with ascites complain of abdominal distention and discomfort. Cardiac tamponade causing pressure equalization in the chambers impairs both filling and cardiac output and can be life-threatening. Signs of tamponade include tachycardia, muffled heart sounds, pulsus paradoxus, and hypotension. Signs of pleural effusions include decreased breath sounds, egophony, and percussion dullness.

B. Laboratory Findings

Malignancy is confirmed as the cause of an effusion when analysis of the fluid specimen shows malignant cells in either the cytology or cell block specimen.

C. Imaging

The presence of effusions can be confirmed with radiographic studies or ultrasonography.


The differential diagnosis of a malignant pleural or pericardial effusion includes nonmalignant processes, such as infection, PE, heart failure, and trauma. The differential diagnosis of malignant ascites includes similar benign processes, such as heart failure, cirrhosis, peritonitis, and pancreatic ascites. Bloody effusions are usually due to cancer, but a bloody pleural effusion can also be due to PE, trauma and, occasionally, infection. Chylous pleural or ascitic fluid is generally associated with obstruction of lymphatic drainage as might occur in lymphoma.


The development of a malignant effusion is a late-stage manifestation of the cancer. Treatment is tailored to the underlying cancer, whether with targeted therapy, chemotherapy, or immunotherapy, depending on tumor testing results. Effective systemic treatment can lead to regression of the effusion. Acute symptoms related to the effusion often require urgent intervention with drainage of the effusion. Decisions regarding palliative management of malignant effusion are in large part dictated by the patient’s symptoms and goals of care.

A. Pleural Effusion

A pleural effusion that is symptomatic may be managed initially with a large-volume thoracentesis. In some patients, the effusion slowly reaccumulates, which allows for periodic thoracentesis when the patient becomes symptomatic. However, in ...

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