Differerent HER2/neu results

[Twocapes]

Diagnosed with 2.5 cm. infiltrating ductal carcinoma, grade II/III with hormone receptors of ER 98%; PR 98%; Ki-67 15%; p53 3% and HER2/neu at 2+.  Requested that the HER2/neu be checked by FISH and it came back as "negative".  I had a lumpectomy with clear margins and sentinel node biopsy which was negative.  I went through four rounds of A/C and over a month of radiation.  Should I be concerned about the different HER2/neu readings?  Also, is much emphasis placed on the Ki-67 (proliferation index)?  
Thank you and thanks for this website - it has been a great help to many.

[Shell1844]

Just have to ask...what does the p53 represent and it's significance to your prognosis?  I was Ki-67 40% and p53 40%.  Unfavorable was listed next to each on my path report?  Does it represent a higher rate of recurrence?
Thank you..

[Twocapes]

Thank you for an easy to understand answer.

[CCF-RN,MSN-rf]

Dear twocapes:  The primary reason for Her2/neu testing in breast cancer is to determine who is most likely to benefit from the drug trastuzumab (Herceptin) which is a monoclonal antibody treatment directed against the Her2/neu protein. There are two common ways to measure HER2/neu status on breast cancer tissue.  One is with Immunohistochemistry (IHC) and the other is the FISH method.  Tumors that are 3+ positive by the IHC testing method and those that test positive by the FISH method are most likely to benefit from trastuzumab.  Tumors that test negative or 1+ by IHC are considered Her2/neu negative and those that test 2+ are considered equivical (in which case FISH testing is typically done to make the determination).  Tumors that test negative for Her2/neu by FISH are unlikely to benefit from trastuzumab. Ki-67 is a measure of tumor cell proliferation and a higher number suggest that a greater number of the tumor cells are in a growth phase and is correlated with somewhat more aggressive behavior.  In general, the entire profile of prognostic markers is more helpful in estimating recurrence risk than any one individual factor although the presence or abscence of lymph node involvement remains one of the most reliable prognostic factors in early breast cancer.