Lung Cancer Biopsy

Diagnosing lung cancer requires a series of tests, beginning with a physical examination and ending with the microscopic examination of lung biopsy tissue samples for cancer cells. Along the way a chest x-ray, CAT scan, thoracentesis, or blood tests may be ordered. The most common diagnostic tools are explained here.

The Physical Examination: Lung Sounds and Lymph Nodes

The diagnostic process starts with your family doctor, who takes a personal and medical history, including your occupation, history of smoking (or exposure to secondhand smoke), and any family history of lung cancer.

A physical exam follows: Your doctor will tap your chest with his or her fingers. This is called percussion, and can reveal unusually dense areas in the chest cavity.

You doctor will also use a stethoscope to listen for lung sounds (the medical term for this is auscultation). Abnormal or unusual lung sounds indicate some form of respiratory problem. Your doctor will also check for swollen lymph nodes in the neck and along the collarbone. Swollen lymph nodes often simply indicate that the body is fighting infection. Alternatively, lymph nodes may be infiltrated with cancer cells if the disease has spread (metastasized).

Chest X-Rays and Sputum Analysis

If the physical exam indicates that further testing is warranted, a chest x-ray or sputum cytology may be ordered. The chest x-ray results are examined for abnormal masses in the lungs. While a positive result may indicate a tumor, it may also indicate smoking scars or other conditions.

In sputum cytology, a sample of mucus brought up by coughing is examined under a microscope for cancer cells and signs of infection. While the test may or may not detect cancer cells, it can suggest the need for further testing.

Diagnostic Imaging: CAT Scans and MRIs

A CAT scan is a sophisticated combination of computer technology and x-rays. Multiple x-rays are taken during a CAT scan, and compiled by computer to form a 3-dimensional image. A CAT scan can detect smaller lung lesions than a standard chest x-ray.

Another diagnostic imaging tool is the MRI, or magnetic resonance imaging. An MRI uses a powerful magnet and radio waves instead of x-rays to build a computerized picture of the internal organs. The MRI signal varies, depending on the nature of the scanned cells.

Other forms of diagnostic imaging, such as radionuclide scanning and bone scans, check if the malignant cells have metastasized and spread to other organs. The stage and spread of lung cancer determines what the treatment options are.

Cancer Cells and Thoracentesis

A build up of fluid between the chest cavity and lungs indicates a medical problem. In a process called thoracentesis the excess fluid is drained off through a special needle. Examination of the fluid may reveal cancer cells.

Blood Tests

Although not used as often as other tests, a variety of blood tests may be used in diagnosis. These tests determine the levels of substances associated with lung cancer. A positive result from any of these blood tests indicates the possibility of lung tumors. These blood tests include:

PTH Testing: Decreased levels of PTH (parathyroid hormone) in the blood help identify lung cancer and rule out other conditions.

CEA (carcinogenic antigen) Testing: High levels of CEA are associated with a variety of cancers. Generally speaking, the higher the CEA level, the more advanced the cancer.

CYFRA 21-1 Testing: CYFRA 21-1 is a protein associated with lung cancer.

Taking a Lung Biopsy Sample

The only certain way to diagnosis lung cancer is to examine the tissue gathered by a lung biopsy. Gathering tissue and cancer cells can be done in several ways. The most common biopsy methods are bronchoscopy and fine needle aspiration.

Diagram of Bronchoscopy ProcedureBronchoscopy: A hollow tube, called a bronchoscope, is threaded through the mouth or nose, down the throat, and into the lungs. During bronchoscopy pictures are relayed back to a monitor, making it possible to examine the diseased tissue directly. If necessary, a small surgical tool at the end of the bronchoscope can retrieve a portion of tissue for analysis.

Transthoracic fine needle aspiration: A long needle is inserted through the chest cavity to collect the biopsy sample. The surgeon uses a CAT scan to guide the needle.

In some cases, it may be necessary to perform a thoracotomy to retrieve biopsy tissue. In this scenario, the chest is opened surgically, and the tissue sample is removed. A thoracotomy allows removal of a larger portion of tissue.

If the doctor suspects that the cancer has spread to the lymphatic system, a sample of swollen lymph nodes may be removed from the neck to be analyzed for cancer cells.

Resources (updated 2002). Lung cancer 101: Diagnosis of lung cancer.

National Cancer Institute. (updated 2002). What you need to know about lung cancer: Diagnosing lung cancer [NIH Publication No. 99-1553].