Does the absence of pleural effusion rule out malignancy (cancer)?

From the Guidelines

The absence of pleural effusion does not rule out the presence of cancer, as many cancers do not cause pleural effusion and the condition has various non-cancerous causes. Pleural effusion is an abnormal buildup of fluid between the layers of tissue that line the lungs and chest cavity, and while it can be associated with certain cancers, such as lung cancer, mesothelioma, and metastatic cancers, many cancers do not cause pleural effusion at all 1. According to a study published in the American Journal of Respiratory and Critical Care Medicine, lung carcinoma is the leading cause of malignant pleural effusions, but malignant effusions are observed in only 7 to 15% of all bronchogenic carcinomas at some time during the course of the illness 1. Additionally, a study published in Chest found that the diagnostic yield for malignancy of pleural cytology is around 72% when at least two pleural fluid specimens are submitted, but the yield from examining more than two specimens of pleural fluid taken on different occasions is low 1. The absence of pleural effusion should never be used alone to rule out cancer, as cancer can present with many different symptoms and clinical findings depending on its type and stage. Some key points to consider include:

• Pleural effusion can have many non-cancerous causes, including heart failure, pneumonia, pulmonary embolism, liver disease, and kidney disease 1
• Cancer can exist in various parts of the body without affecting the pleural space 1
• A comprehensive cancer diagnosis typically requires specific imaging studies, biopsies, blood tests, and other diagnostic procedures targeted to the suspected type and location of cancer 1
• The diagnostic yield for malignancy depends on sample preparation, the experience of the cytologist, and the tumor type, with the highest diagnostic yields retrieved in patients with adenocarcinoma 1.

From the Research

Pleural Effusion and Cancer

• The absence of pleural effusion does not necessarily mean that there is no cancer, as cancer can be present without causing a pleural effusion 2, 3, 4.
• Pleural effusions can arise from a variety of conditions, including systemic, inflammatory, infectious, and malignant diseases 2.
• The presence of a malignant pleural effusion indicates advanced disease and poor survival, and is often associated with lung or breast cancer 3, 4.

Diagnosis of Pleural Effusion

• The diagnosis of pleural effusion depends on a combination of medical history, physical examination, imaging tests, and pleural fluid analyses, including specific biomarkers 2.
• Thoracic imaging, such as computed tomography or ultrasound, can be helpful in distinguishing malignant from benign effusions 3, 4.
• Pleural fluid cytology is diagnostic in about 60% of cases, and pleural biopsies may be helpful in cytology-negative disease 4.

Relationship between Pleural Fluid Appearance and Cancer

• The appearance of pleural fluid (e.g., bloody or non-bloody) does not predict the etiology of the effusion in patients with cancer and recurrent symptomatic pleural effusions 5.
• The presence or absence of blood in pleural effusions cannot predict their etiology in patients with cancer 5.

Treatment of Pleural Effusion

• The treatment of pleural effusion depends on the underlying cause and can range from pleurodesis to thoracoscopy and video-assisted thoracoscopy, to the placement of a permanently indwelling pleural catheter 3, 4, 6.
• The proper treatment of pleural effusion can only be determined after meticulous differential diagnosis 6.