A cytology exam of pleural fluid is a laboratory test to detect cancer cells and certain other cells in the area that surrounds the lungs. This area is called the pleural space. Cytology means the study of cells.
How the Test is Performed
A sample of fluid from the pleural space is needed. The sample is taken using a procedure called thoracentesis.
The procedure is done in the following way:
- You sit on a bed or on the edge of a chair or bed. Your head and arms rest on a table.
- A small area of skin on your back is cleaned. Numbing medicine (local anesthetic) is injected in this area.
- The doctor inserts a needle through the skin and muscles of the chest wall into the pleural space.
- Fluid is collected.
- The needle is removed. A bandage is placed on the skin.
The fluid sample is sent to a laboratory. There, it is examined under the microscope to determine what the cells look like and whether they are abnormal.
How to Prepare for the Test
No special preparation is needed before the test. A chest x-ray will likely be done before and after the test.
Do not cough, breathe deeply, or move during the test to avoid injury to the lung.
How the Test will Feel
You will feel stinging when the local anesthetic is injected. You may feel pain or pressure when the needle is inserted into the pleural space.
Tell your health care provider if you feel short of breath or have chest pain.
Why the Test is Performed
A cytology exam is used to look for cancer and precancerous cells. It may also be done for other conditions, such as identifying systemic lupus erythematosus cells.
Your doctor may order this test if you have signs of fluid buildup in the pleural space. This condition is called pleural effusion. The test may also be done if you have signs of lung cancer.
Normal cells are seen.
Risks are related to thoracentesis and may include:
- Collapse of the lung (pneumothorax)
- Difficulty breathing
Pleural fluid cytology; Lung cancer - pleural fluid
Blok BK. Thoracentesis. In: Roberts JR, Custalow CB, Thomsen TW, eds. Roberts and Hedges' Clinical Procedures in Emergency Medicine and Acute Care. 7th ed. Philadelphia, PA: Elsevier; 2019:chap 9.
Cibas ES. Pleural, pericardial, and peritoneal fluids. In: Cibas ES, Ducatman BS, eds. Cytology. 5th ed. Philadelphia, PA: Elsevier; 2021:chap 4.
Chernecky CC, Berger BJ. Thoracentesis - diagnostic. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. St Louis, MO: Elsevier Saunders; 2013:1052-1135.
Review Date 8/3/2020
Updated by: Denis Hadjiliadis, MD, MHS, Paul F. Harron Jr. Associate Professor of Medicine, Pulmonary, Allergy, and Critical Care, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.