It is collection of fluid in chest / lung cavity. A person having this problem may have heaviness in chest or chest pain or breathing difficulty. The most common causes of pleural effusion are tuberculosis, heart disease, kidney diseases and lung cancer. Most of the time these patients are considered to have tuberculosis and are treated wrongly. Lung Cancer and other cancer can cause pleural effusion too. So, if you come across with such patients, kindly ask them to get examined to rule out any possibility of Lung Cancer.