Would you give a HER2 targeted agent to a patient whose initial cancer was ER/PR positive, HER2 negative but now with metastatic disease that is ER positive, PR negative, HER2 2+, FISH equivocal?   

Discordance of HER from primary to metastatic status is seen in about 5-10% of cases (1). Little data are available regarding outcomes of these cases, but responses have been seen in patients with HER2-negative primary tumors and HER2+ metastases (2), and I have certainly observed this personally. I...