what to look for

I was told I had breast cancer in 2008.   I went for a mammogram and they found a spot in each breast the left one came back benign but the right one was cancer so the surgeon removed the spot and while she was at it she removed the lymph nodes on the left to supposedly remove the risk of reoccurring. all it seemed was good for a year and then a lump appeared on my left breast I had my mammogram and a biopsy done and the results were clean. The lump got bigger so there was another mammogram and biopsy still the results came back clean.  My surgeon said then that she was just going to take it out anyway so there was yet another mammogram done and a date was set for surgery which was just this last Wed. and as I am recovering the surgeon came to tell me that "she was so sorry"  because as she was removing the lump that there was a cancer spot apparently hiding underneath. How common is this is my question,and with all of the mammograms and biopsys why wasn't this seen.  Thank You Debby

[Cleveland Clinic]

Dear debbysue:  This is uncommon.  However, a needle biopsy is only as good as the tissue contained withing the needle.  So, if there is a small spot of cancer within a larger lump, a needle biopsy could easily miss it.  Removing the lump removes all the tissue so there is much less possibility of missing the problem.  A mammogram is a test that may show a mass, but it cannot tell us if it is cancer or not - only if it is suspicious.