Fat necrosis imaging can be confusing initially. The key is to keep in mind the pathology involved. The imaging is a spectrum that ranges from an oil cysts to partial calcification the dense widespread, alarming balls of calcium in the breast. It just depends at which stage of te process you are imaging the breast.
The secret is to know the surgical (or trauma) history and to have previous for comparison. I always add ultrsound and the ultrsound imaging is very typical. Note in the mammogram image the spiculation from the reaction and fibrosis following surgey; you can see this on ultrasound too.
Train your eye to spot and follow fat necrosis is the surgically reduced breast; after a while you spot them immediately. Remember the fat necrosis can be a way from the scar they do not have to be directly contigous.
The wide spectrum of appearances of fat necrosis is the key to getting at the diagnosis. That and the history. The images can progress and change with time, sometimes years after the surgery.