Malignant pleural effusion is caused by cancer cells growing in the pleural cavity, causing damage and leading to effusion. Malignant pleural effusion is a treatable disease, however, the disease often progresses to a more severe stage, threatening the patient's life.

Currently, there are many laboratory methods to help diagnose pleural effusion accurately and easily, even in the case of small pleural effusion, malignant pleural effusion. To diagnose pleural effusion, it is necessary to rely on clinical and subclinical symptoms.

When there is more fluid than normal in the pleural cavity, it is called a pleural effusion. Pleural effusion can occur in both adults and children.

Pleural effusion is not a disease but a syndrome caused by many different diseases. To diagnose pleural effusion as well as the cause of this condition, pleural effusion tests need to be done.