Antibody and Molecular Testing

Reviewed by: HU Medical Review Board | Last reviewed: January 2017.


Immunohistochemistry is a type of laboratory testing that uses antibodies to test for certain markers, or antigens, in a sample of tissue. The antibodies are able to interact with specific antigens, followed by staining with fluorescent dye that binds to its respective antibody, allowing the presence of the specific antigen to be seen in cells under a microscope. Immunohistochemistry is used to help diagnose lung cancer as well as other diseases. It can also be helpful in distinguishing among different types of lung cancer.1

Types of Lung Cancer

There are several different types of lung cancer, notable for their clinical and biologic differences. Different types of lung cancer also have variations in their growth pattern, propensity to spread or metastasize to other parts of the body, prognoses (projected outcomes), and require different treatment. The most common type of lung cancer is non-small cell lung cancer (NSCLC). NSCLC accounts for approximately 85% of all lung cancers. Within the category of NSCLC are several additional classifications, including adenocarcinoma, squamous cell carcinoma, large cell carcinoma, adenosquamous carcinoma, and sarcomatoid carcinoma. Small cell lung cancer accounts for approximately 15% of all lung cancers. SCLC is an aggressive, rapidly growing cancer, and it is likely to invade surrounding tissues and metastasize to other areas of the body. Lung carcinoid tumors make up less than 5% of all lung cancers and tend to be slower growing. Because they are made up of neuroendocrine cells, they are also known as lung neuroendocrine tumors.1-3

Molecular Testing

Molecular testing is laboratory testing done on a sample of a malignant (cancerous) tumor to detect genetic mutations. Changes in the genes can cause normal cells to become cancer cells. Genetic changes can be inherited, but in the case of lung cancer, the genetic changes that cause cancer to develop can be caused by other factors, such as environmental exposure to pollutants like tobacco smoke. Scientists have found that there are certain changes, or mutations, that commonly occur in many lung cancers. These mutations are often a target for potential treatments to halt and eliminate the lung cancer. Some of the identified genetic mutations found in lung cancer that can be tested for in molecular testing include:

Guidelines for Molecular Testing

Identifying the molecular specifics of lung cancer has led to more personalized treatments in the form of targeted therapies. However, a significant portion of lung cancer patients do not get their tumors analyzed for these genetic abnormalities upon diagnosis, which has led to the creation of guidelines for physicians. The guidelines, created in 2013 by the College of American Pathologists, the International Association for the Study of Lung Cancer, and the Association for Molecular Pathology, set standards for the minimum level of genetic testing in patients with lung adenocarcinoma. The guidelines recommend that all patients with advanced lung adenocarcinoma should be tested for abnormalities in EGFR and ALK, regardless of other clinical variables such as sex, race, or smoking history. Approximately 20-25% of patients with lung adenocarcinoma are believed to have one of these two genetic mutations, and targeted therapies are available for both of these abnormalities.5,6

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