Leukemia after a clear peripheral smear?

My 5-year-old daughter has an agressive lump in her breast, which was stated to be possible leukemia or lymphoma.  We found it 1 month ago.  

She has had numerous CBCs that have come back irregular in the past and had a peripheral smear last fall that came back wnl.  She also had a CBC wnl 2 months ago.  

How likely is it that leukemia or lymphoma could be the diagnosis?

Thank you.

[CCF-RN,MSN-rf]

Dear dayzt:  The medhelp forum addresses questions about breast cancer - and this is our expertise.  In a 5 year old, breast cancer is virtually unheard of.  If there is a breast lump that is malignant, it is more likely to be associated with a lymphoma or leukemia or some other childhood cancer.  The only way to know for certain may be to do a biopsy.