discrepant results Oestrogen receptor status

HI, I'm just wondering if anyone else has had something like this -- I was diagnosed by core biopsy at a highly reputable hospital, oestrogen receptor 80% positive and neg for the other two (progesterone and HER). Because I made a choice to be treated in a different city, my pathology slides were sent from the original hospital to the second hospital, where these same biopsy slides were re-read as triple negative. Then in late December I had a lumpectomy, and the pathology result for the tumor itself was 95% oestrogen positive and neg for the other two. Does this kind of thing happen often? Has anyone heard of the same set of slides being read first as pos and then as neg for oestrogen receptor? Just to be clear, both places have great reputations. Also, we are not talking about years later, the tumor characteristics changing. All these results came within 6 weeks of the original biopsy. I'm now waiting on Oncotype dx results. This kind of thing makes me less confident about results in general.