Malignant Pleural Effusion Explained

Each lung is wrapped in a thin tissue layer called the pleura. Another layer lines the inside of the chest wall. The narrow gap between them is the pleural space.

That gap is not meant to be empty. The National Cancer Institute says it holds "a small amount of fluid that helps the lungs move smoothly in the chest while a person is breathing." Think of it as a film of oil between two sheets of glass.

A pleural effusion is extra fluid in that gap. MedlinePlus defines it as "a buildup of fluid between the layers of tissue that line the lungs and chest cavity." It is called malignant when cancer is the reason.

The fluid does not fill the lung. It presses on it from outside. The lung cannot expand fully, so a breath brings in less air. That is why the first sign is usually breathlessness rather than pain.

NCI notes that "lung cancer, breast cancer, lymphoma, and leukemia cause most malignant effusions." Other things can add to the fluid. NCI lists radiation therapy, chemotherapy, a collapsed lung, and cancer that has spread to lymph nodes, and adds that some people with cancer have conditions such as congestive heart failure, pneumonia, a blood clot in the lung, or poor nutrition that may lead to a pleural effusion.

NCI lists three signs: shortness of breath, cough, and chest discomfort or pain.

MedlinePlus adds detail. Chest pain is often sharp and worse with a cough. Breathing may be fast. Fever and hiccups can occur. Some people have no symptoms at all, and the fluid turns up on a scan done for another reason.

Breathlessness that builds over days is the pattern people describe most. Stairs get harder. Then flat ground. Then lying flat at night.

A chest x-ray usually shows the fluid. NCI also lists CT scan and ultrasound. Ultrasound is often used at the bedside to mark a safe spot before a needle goes in.

Seeing fluid is not the same as knowing why it is there. For that, a sample is needed.

The sample comes from a thoracentesis, sometimes called a chest tap. MedlinePlus describes it simply. "A sample of fluid is removed with a needle inserted between the ribs." ACS adds that the doctor numbs an area in the lower back first.

The lab checks that fluid for cancer cells, infection, protein, cell counts, and acidity. NCI lists flow cytometry as another lab test, which sorts and identifies cells. If the tap does not answer the question, NCI notes a biopsy may be taken using thoracoscopy, a camera passed into the chest through a small cut.

Thoracentesis is a treatment as well as a test. Taking the fluid off relieves pressure and makes breathing easier.

The relief is real but usually temporary. NCI puts it bluntly: "A few days after the extra fluid is removed, it is likely it will begin to come back." Cancer in the pleura keeps producing fluid, so drainage alone does not stop the process.

NCI lists the risks of the procedure as bleeding, infection, a collapsed lung, fluid in the lungs, and a sudden drop in blood pressure. A collapsed lung, or pneumothorax, means air has leaked into the pleural space.

Because of the return rate, the real decision is usually not whether to drain once. It is what to do about the third or fourth time.

Pleurodesis works by removing the space itself. If the two layers stick together, there is nowhere for fluid to collect.

ACS describes the chemical version. A chest tube goes in through a small incision. Then "a substance is put into the chest through the tube that causes the linings of the lung (visceral pleura) and chest wall (parietal pleura) to stick together." Agents named by ACS are talc, doxycycline (an antibiotic), and bleomycin (a chemotherapy drug). NCI names bleomycin and talc.

There is also a surgical version. ACS describes talc being "blown into the space around the lungs during an operation," done through thoracoscopy via a small incision.

Pleurodesis needs a chest tube and time in hospital while the lining seals. When it works, it is a one-time fix. It works best when the lung can expand fully after drainage, because the two surfaces have to touch to stick.

The other approach keeps the space and manages the fluid instead.

NCI describes an indwelling pleural catheter, or IPC, as a small tube that is inserted and left in place to keep fluid from building up around the lungs. It says the catheter may be used for long-term care so that a separate procedure will not have to be done each time draining is needed. ACS describes the same device: one end sits in the chest through a small cut in the skin, and the other end stays outside the body.

Fluid is drained at home into bottles on a schedule the team sets. No needle each time. No hospital stay for each drainage.

NCI lists infection and blockage as the risks.

The trade-off between the two is real. Pleurodesis aims to end the problem but needs a hospital stay and a lung that re-expands. A catheter needs no hospital stay but stays with you, with supplies, dressings, and a routine.

NCI also lists two surgical options: a shunt, a tube that diverts fluid into the abdomen, and pleurectomy, removal of the pleural lining.

NCI is clear that the aim is usually palliative. That means treatment is chosen "to relieve signs and symptoms and improve quality of life." It is not the same as giving up on cancer treatment. Systemic cancer treatment often continues at the same time.

• Shortness of breath or difficulty breathing right after a thoracentesis. MedlinePlus names this specifically as a reason to "contact your provider or go to the emergency room." It can mean a collapsed lung.
• Breathlessness that comes on suddenly, or that is there at rest.
• Chest pain with breathlessness, or breathlessness with a fast heartbeat.
• Lips or fingertips turning blue or grey.

• Breathlessness that is clearly worse than last week, even if it is not severe yet.
• Needing more pillows at night, or having to sleep sitting up when you did not before.
• A temperature of 100.4°F (38°C) or higher, which is CDC's threshold for people with cancer. CDC notes that "fever may be the only sign that you have an infection." Also call if the drainage site becomes red, hot, painful or starts leaking.
• A new cough, or coughing that will not settle.
• Fluid that changes color, turns cloudy, or smells.
• A catheter that stops draining while your breathing is getting worse.

• National Cancer Institute — Cardiopulmonary Syndromes (PDQ) Patient Version
• MedlinePlus — Pleural effusion
• American Cancer Society — Palliative Procedures for Non-Small Cell Lung Cancer
• CDC — Watch Out for Fever (Preventing Infections in Cancer Patients)