My doctor used fat transfer to fill the depression left by lumpectomy, and now the area is hard & discolored. what happened?

My guess is...: Fat necrosis. As a living tissue, fat needs a blood supply to survive. The unpredictability of fat grafting comes from the inability to assure a good blood supply, especially if your lumpectomy was accompanied by radiation treatment. Because concern always accompanies lumps in breasts previously treated for cancer, you should see your doctor for an examination.

Talk to your surgeon: Best advice is to talk to your plastic surgeon. Without examining you or knowing more info, i can't really say for certain. If it is hard and discolored, it could be bruising or hematoma or an infection, etc, but again, i would call your surgeon. Most surgeons want to hear from their patients if there are problems or questions.

Depends: Get seen by the doctor who did the transfer. It depends on how long has it been since the fat transfer. Best to have it examined by that physician. Best wishes.