HER2-negative breast cancer means tests show no abnormality in the human epidermal growth factor receptor 2 gene. Normally present in breast tissue, HER2 receptors help control how breast cells grow and divide. When the gene stops functioning properly, breast cells begin to multiply in an uncontrolled way, states Breastcancer.org.
A disruption in HER2 gene function is present in about 25 percent of breast cancers, reports Breastcancer.org. These cancers, which are known as HER2-positive breast cancers, grow faster, spread more readily and recur more often than cancers that are HER2-negative.
HER2 status is an important factor in determining breast cancer treatment, explains Breastcancer.org. Since laboratory standards differ, the organization recommends that women whose cancer tests HER2-negative discuss with their doctors whether confirming the results with a second test is a good idea.