This image is an H&E stained section of breast with tumor. Tumor areas in H&E slides are marked by the pathologist for subsequent IHC and FISH testing (not shown in this image).
It is critical that analysis be conducted on the invasive component of the breast cancer. This is because HER2 is, for unclear reasons, frequently increased (overexpressed and/or over amplified) in ductal carcinoma in situ (DCIS), and the clinical implications of this finding are uncertain.