I don't know about lighting up a scan but when I was on the phych's happy pills they made my nodes under the unaffected arm swell up. It sent my surgeon and oncology doc scurrying for an ultrasound and they told me to get off the pills. The nodes went down and there was no probs.
I have a protruding bit of bone in the front of my chest so my surgeon did and xray but that turned out to be a quirky thickening of the rib where I only have 3mm of skin over it and it bruises easily. I just have to be careful of it.
For years they have been observing a cyst in my unaffected breast when it is scanned and measured. Nothing has ever come of it.
I do get thickening under the axillary clearance arm but on lymph massage and sometimes a compression sleeve, that goes away by itself.
It's all a bit worrying but no word on the big C so I am happy.