Various laboratory tests are employed to test for abnormal genes and proteins in tumor samples. The selection of a test depends on which specific abnormality is being investigated, the type of sample available, and the reliability of the testing method.
Immunohistochemistry (IHC) is used to test for the amount of protein in a sample. The method is based on antibodies, which are immune-system proteins that bind to specific targets, like a key fitting into a lock. The antibody molecule is combined with a molecular stain so that when the antibody is applied to a biological sample and binds to its target, its presence can be detected using a microscope (the portions containing the protein will appear darker).
Fluorescence in situ hybridization (FISH)
Fluorescence in situ hybridization (FISH) is a powerful technique used to detect specific genetic sequences (short sections of DNA or RNA) inside cells. FISH is used to detect missing or extra copies of genes, as well as abnormal positioning of a gene within chromosomes.
Polymerase Chain Reaction (PCR)
Polymerase Chain Reaction (PCR) is a method used to detect specific genetic sequences. PCR can amplify a specific genetic sequence, such as a cancer-causing gene mutation. A biochemical chain reaction is used to make millions of copies of the target sequence, thereby producing enough to be detected.
Circulating tumor cell analysis (CTC analysis)
Circulating tumor cell analysis (CTC analysis) is a newly developed technique that allows doctors to isolate tumor cells from a simple blood sample and analyze them for biomarkers (12). This technique will allow patients to be tested for certain markers (e.g. EGFR mutations) without the need for invasive surgery, thereby broadening the scope of patients who may benefit from such testing. In addition to its use in initial screening, CTC analysis may allow physicians to monitor patients' tumors regularly in order to rapidly detect the emergence of resistance mutations and tailor treatment accordingly (12). CTC analysis is currently an approved method for predicting responses to treatments in a variety of other cancers, including breast and prostate cancers.