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Biomarker testing, in plain language

Biomarker tests look at the genes and proteins in your cancer, and they can open the door to treatments made for your exact cancer. If all the letters and numbers feel overwhelming, you're not alone. Pick a test below to learn what it means for you and your family.

ℹ️ General information to help you and your loved ones talk with your care team, not medical advice. Read our disclaimer.

Tissue vs. blood

Most tests use a piece of tumor tissue from a biopsy or surgery. Some can also use a blood sample (a 'liquid biopsy') that looks for tumor DNA floating in the blood. Blood tests are easier and faster, but they can miss a change that a tissue test would find, so a negative blood test is often followed by a tissue test.

By cancer type

Breast cancer

ER/PR (hormone receptors), HER2, BRCA1 and BRCA2, PIK3CA, PD-L1

Lung cancer

EGFR, ALK, ROS1, KRAS (including G12C), BRAF, MET, RET, NTRK, PD-L1

Prostate cancer

PSA (prostate-specific antigen), AR and PSMA, BRCA1 and BRCA2, HRD (homologous recombination deficiency), MSI-H / dMMR

Colorectal cancer

MSI-H / dMMR, KRAS (including G12C), BRAF, HER2, NTRK

Ovarian cancer

BRCA1 and BRCA2, HRD (homologous recombination deficiency), MSI-H / dMMR

Browse biomarker tests

Written by the Cancer Side Effects Guide team from FDA labels and leading cancer centers. Not medical advice. · Last updated: October 15, 2026 · How we write