Let's have a look at the technologies that are used to detect genetic alterations in patients with CRC. Select each of the test types below for a description.

Test	Description
Immunohistochemistry (IHC)	Uses antibodies that attach to specific proteins (antigens) that may be on the surface or within cells Has antibodies designed to bind with cancer-specific antigens Contains chemicals to induce a color change when the antibody binds with antigen, making the antigen-bearing cells visible Used to classify certain cancers, since binding will only occur if an antigen specific to the cancer type being tested is present Can also test for the presence of cancerous cells in areas outside of the tumor, such as lymph nodes
Fluorescence in situ hybridization (FISH)	Detects specific parts of certain chromosomes within the cell Has fluorochrome-labeled DNA sequences, called probes, that bind to complementary DNA sequences in the cell Can detect gene amplification, deletions or duplications, rearrangements, and other genetic aberrations
Polymerase chain reaction (PCR) and reverse transcriptase PCR (RT‑PCR)	Detects specific DNA or RNA sequences associated with specific cancers Amplifies (ie, makes multiple copies of) DNA or RNA segments isolated from tumor cells Can detect specific sequence coding for proteins that are present in cancer cells, but not in normal cells
Next-generation sequencing (NGS)	NGS refers to technology in which millions of nucleotide sequences are deciphered simultaneously Advances in NGS have allowed for more comprehensive testing of multiple gene mutations of interest in CRC NGS can detect single nucleotide variants, copy number variations, gene fusions, and other abnormalities Sometimes reveals unexpected mutations that may inform therapeutic decisions