Cancer biomarkers & molecular testing
Molecular-testing and pathology reports name biomarkers — genes and proteins measured in the tumor — that inform how a cancer is characterized. Each page below explains, factually and with authoritative sources, what a marker is and why it is tested. This is general information, not medical advice: what any result means for you is a question for your oncologist.
ALK (anaplastic lymphoma kinase)
ALK (anaplastic lymphoma kinase) is a gene whose protein is a receptor tyrosine kinase; certain changes in the gene — such as ALK rearrangements — can keep the protein persistently active and contribute to some cancers.
ROS1
ROS1 is a human gene that codes for a receptor tyrosine kinase; a rearrangement of the ROS1 gene is used as a tumor marker in non-small cell lung cancer.
KRAS
KRAS is a gene that carries instructions for making the K-Ras protein, part of a cell-signaling pathway (RAS/MAPK) that helps control cell growth and division.
BRAF
BRAF is a human gene that makes a protein called B-RAF, which helps send signals inside cells and is involved in cell growth.
HER2 (ERBB2)
HER2 (ERBB2) is a protein found on the surface of cells that helps control cell growth, and which some cancers make in larger-than-normal amounts.
PD-L1 (programmed death-ligand 1)
PD-L1 (programmed death-ligand 1) is an immune-regulating protein, encoded by the human CD274 gene, that helps control the activation and proliferation of the immune system's T cells.
BRCA1 and BRCA2
BRCA1 and BRCA2 are human genes that make proteins which help repair damaged DNA, and harmful inherited changes in them raise the risk of certain cancers.
EGFR (epidermal growth factor receptor)
EGFR is a gene that provides instructions for a cell-surface receptor protein that relays growth signals into the cell; certain EGFR gene changes are found in some cancers and can be identified by biomarker testing.
MSI-H / dMMR (microsatellite instability-high / mismatch-repair deficiency)
A tumor state marked by genomic instability from defective DNA mismatch repair, detected as high microsatellite instability (MSI-H) or loss of mismatch-repair proteins (dMMR).