Are ER and HER2 determined by blood tests?

Are ER and HER2 determined by blood tests?

• A. Sometimes
• B. No
• C. Yes
• D. Only for ER

Answer: (B)

ER and HER2 status come from the tumor cells themselves, not from the blood. To determine whether a breast tumor is ER-positive or HER2-positive, pathologists analyze tissue from a biopsy or surgery using immunohistochemistry, and for HER2 they may use additional tests like FISH if the IHC result is unclear. Blood tests don’t measure receptor expression on tumor cells, so they can’t determine ER or HER2 status. Blood-based tests can help monitor disease or detect other markers, but they don’t replace tissue testing for guiding endocrine therapy or HER2-directed treatments.

ER and HER2 status come from the tumor cells themselves, not from the blood. To determine whether a breast tumor is ER-positive or HER2-positive, pathologists analyze tissue from a biopsy or surgery using immunohistochemistry, and for HER2 they may use additional tests like FISH if the IHC result is unclear. Blood tests don’t measure receptor expression on tumor cells, so they can’t determine ER or HER2 status. Blood-based tests can help monitor disease or detect other markers, but they don’t replace tissue testing for guiding endocrine therapy or HER2-directed treatments.