The methodology described in this course is from the Agilent Dako HercepTest™, as used with the Dako "classic" automated staining instrumentation with antigen recovery being performed outside of the instrument. Antigen recovery is necessary to release the aldehyde bonds caused by formalin fixation. Heat-induced epitope retrieval (HIER) is performed in a water bath at 100º C for 40 minutes using a citrate buffer. Polymer technology is used to reduce biotin related background and to increase the signal. The polymer is based on dextran technology and consists of both secondary goat anti-rabbit IgG and horseradish peroxidase molecules linked to a common dextran polymer.