secondary cancer

I know secondary (spread from somewhere else in the body) cancer in the breast is very rare but when testing a biopsy sample would this be spotted or would they just be testing for breast cancer and not pick up on other cancer cells. As i said before we are finding it strange that my Moms breast cancer cannot be diagnosed for sure.

[CCF-RN,MSN-rf]

Dear jessicat:  A biopsy is generally done to identify the type of cancer cells, regardless of their origin.  Sometimes a biopsy either does not have enough tissue to make this judgement or the cells are so "mutated" that they do not resemble any particular cell.  In these cases, the cancer may be classified as an unknown primary.  Metastasis to the breast is, indeed, rare, but not impossible.

[fae]

My wife was just diagnosed with a very rare form of breast cancer. It took 6 weeks of examines to determine with confidence that it was breast cancer and not cancer from another site. We did every exam you can imagine, finishing with a P.E.T. scan. Her cell type was determined to be "clear cell" which is almost never found in the breast.  All tests came back negative for cancer out side the breast, so we are proceeding under the asumption that she has breast cancer....a very rare case.  So I understand your concern and frustration in trying to identify what it is you are facing.