[SandyBB]

Rachel, cellulitis such as your mom's, and with her history, is usually caused by lymphedema. Lymphedema results when there are too few nodes in the area (i.e. removed during the cancer surgery) or when the nodes are damaged from radiation. Lymph fluid can not travel effectively through the lymph vessels in the area and this can cause the arm (or breast or underarm area) to swell. If the fluids continue to build up, they can become infected and turn into cellulitis.
This happened to me last year after a bad cat scratch - lymph fluids are used to battle infections so the cat scratch activated the fluid production but the nodes I had left in the area are damaged from direct radiation so the fluid did not flow correctly and ended up backing up in my upper arm, causing an infection. In my case, I was put on strong antibiotics and began aggressive lymphedma treatment once the infection had cleared. (see my previous note in this thread).

I am not sure if you were inferring this/afraid of this, but cellulitis has NOTHING to do with your Mom's cancer returning. It is a serious condition and will mean she needs to also aggressively treat her lymphedema, but it in NO WAY is related to her prognosis of staying cancer free.
Take care,
Sandy