Fat necrosis within the breast is a pathological process that occurs when there is saponification of local fat. It is a benign inflammatory process and is becoming increasingly common with the greater use of breast conserving surgery and mammoplasty procedures. Fat necrosis is a benign (non-cancerous) breast condition that happens when an area of the fatty breast tissue is damaged, usually as a result of injury to the breast.. It can also happen after breast surgery or radiation treatme. If you feel a lump in your breast, it may be fat necrosis. Fat necrosis is a lump of dead or damaged breast tissue that sometimes appears after breast surgery, radiation, or another trauma.