Recurrence during treatment??

oldlady

Can a lump form in the healthy breast while you are undergoing active treatment for the malignant one? I had a lumpectomy, re-excision, 4 tx of TC chemo, and am about 1/2way through radiation. I am supposed to start Tamoxifin after the radiation. My oncotype was literally on the border between low and intermediate risk cutoff.  My tumor was ER/PR+, Stage 2, Her2Neu Neg.  I am in my mid40s and I am the first female on either side of my family diagnosed with BC.  However, I felt something odd last night and of course do not want to overreact.