What tests may confirm sarcoidosis?
Ask the doctor
Q. I probably have sarcoidosis. Is a lung biopsy always needed?
A. Sarcoidosis is an illness that causes tiny islands of inflammatory cells to form throughout the body. These microscopic groups of cells are called granulomas. They are especially common in the lungs, lymph nodes, skin, eyes, and liver.
We don't know what causes sarcoidosis. But we do know what it looks like under the microscope. That's why a biopsy is usually needed to confirm the diagnosis.
When a lung imaging test like a chest x-ray or CT scan shows changes that could be due to sarcoidosis, doctors first look for any easier places to biopsy rather than the lung. Examples include:
- a new brown bump on your skin
- an enlarged lymph node
- a tiny bump on the inside surface of your eyelid.
However, a lung biopsy is often required.
A lung biopsy might sound scary, but it is actually relatively safe when performed by a doctor with training and experience. The type of lung biopsy done most often to diagnose sarcoidosis is called bronchoscopy with a transbronchial biopsy. The bronchoscope is a flexible tube with a light and small camera on the tip of the instrument.
During bronchoscopy, the tube is inserted through the mouth or nose. The doctor slowly passes the bronchoscope down into the trachea (windpipe) and bronchi (large air tubes leading from the trachea to the lungs). To limit discomfort, you will likely receive a light sedative. Your mouth or nose is numbed with a local anesthetic beforehand.
The doctor watches on a screen as the camera advances into one of the bronchi. A wire with a pincher on the end is passed through the bronchoscope. The doctor opens and closes the pincher to take a sample of lung tissue. This is usually repeated to get a few different samples. The procedure takes about 45 minutes. The samples are sent to the laboratory to be examined under the microscope.
As you should with any invasive test, ask the doctor to explain the possible complications before you sign the consent form.
Image: © athima tongloom/Getty Images
About the Author
Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
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