Ideally fat transfer to the breast should not interfere with mammograms and that is why the procedure is done. Given your history of breast cancer on the other side I think this situation should be evaluated by your oncologist or surgeon with perhaps stereoscopic biopsies to ascertain nothing adverse is going on.
Fat transfer to the breast
Fat transfer to the breast is very technique dependent. You have to imaging treating the breast like a piece of Swiss cheese. The fat needs to placed in small droplets at various depth to allow the fat cells to survive. If a large piece of fat is transferred all at once and there is not good surrounding vascular tissue the fat will die and end up with a condition called fat necrosis. This leads to lumpiness of the grafted fat. Occasionally this can create calcifications in the breast. This may worry the radiologist as cancer can be associated with calcifications in the breast. They type of calcification associated with fat necrosis appears to be different compared with the calcifications associated with breast cancer. When too much fat is transferred at one time fat necrosis may occur. So you have to monitor what's happening to the fat as some of the fat necrosis will reabsorb over time.
Lumpy breasts after fat transfer
Lumpy breasts after fat transfer can be due to large volumes of fat being placed in a single area with subsequent fat necrosis (death of the transferred fat) rather it being placed in small droplets to try to enhance the fat graft's ability to acquire a blood supply and survive. Fat grafting has been shown to not confuse the detection of breast cancer on mammograms. Perhaps another type of study such as mammogram or MRI may help address your concerns. You should discuss this with your plastic surgeon.
Lumps in breast after fat transfer
Unfortunately, the success of fat transfers cannot always be predicted. The lumpiness can be from calcification of the fat or simply uneven distribution of the fat. While many surgeons have had success with fat transfers, there is still some controversy over its use,
especially with regard to following breast cancers.
The PET scan measures cellular activity of the tissue. Thus, increased activity may be present as your own cells are trying to break down the clumps of fat.
I would advise you strongly to check with your surgeon to be sure everything is OK.
Hope this helps,