[RobinP]

Sure can change John. That's why serum her2 test is so important in the evaluation of treatment for patients that have MBC;know if they need herceptin or not. See Joe's article her serum test. Also, think how many initial pathologies are misread that we never know about, with those thinking that they were her- when they were all along her2+ . Then again, some her- initial tumors may evolve and change to positive on their own; this is currrently a great area research interest.