The page below is a sample from the LabCE course HER2 Testing in Breast Cancer. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

Learn more about HER2 Testing in Breast Cancer (online CE course) »
How to Subscribe
Histology CE Package$65 Add to cart

HER2 Fluorescence in Situ Hybridization (FISH) Interpretation


  1. Read 20 cells, document the copy number of the HER2 gene (orange) and the copy number of the centromere 17 signal (green).
  2. Calculate the average copy number of each, per cell.
  3. Calculate the average ratio of HER2 to centromere 17.
  • NEGATIVE for amplification: HER2 ratio <2.0 with an average copy number of <4.0 signals/cell
  • POSITIVE for amplification: HER2 ratio > 2.2
  • EQUIVOCAL: <2.0 with an average HER2 copy 4.0 and <6.0 signals/cell.