Fat necrosis?

I had a lumpectomy, Chemo (CEF) and radiation treatment which finished in April. I now have a small lump in my incision. I saw the surgeon who did a needle biopsy and thinks that its fat necrosis. What causes the fat necrosis - could it be the radiation, or scar tissue??. Do you know if it reabsorbs into the breast? I really don't want more surgery. I am scheduled for a mammogram and breast ultrasound in a few weeks and wondering if it shows up in these tests.
I heard of fat necrosis from trauma to the breast so is radiation or surgery considered trauma...?
Thanks in advance for your response....
Fuzzy

[CCF-RN,MSN-JS]

Dear Fuzzy, Fat necrosis means that the tissue removed is dead tissue, possible causes could be radiation or scar tissue formation.  Any event, which causes damage to the body, can be considered trauma.  For example, the surgical incision can be trauma to the skin.  

In a mammogram or sonogram this lump in the incision may show up as an abnormality, however the only way of determining that it was fat necrosis is by examining the tissue under the microscope.  Having this area removed surgically may be indicated to improve the cosmetic result, relieve discomfort, or if it was deemed necessary, once the ultrasound and mammogram results are in, to examine more of the tissue under the microscope.