What are ways of treating fat necrosis after breast reduction/lift? (photo)

It is most likely fat necrosis , scar tissue, or old encapsulated hematoma. Needle biopsy can help with diagnosis but may not be at this stage not necessary. I would recommend to my patients a vigorous massage program to see if it can be softened more over the next 3-6 months. Keep your yearly mammogram appointment. further workup could consist of ultrasound, CT or MRI . 

is usually allowed to diminish on its own.  If breasts are near equal in volume, my patients are asked to be patient as the size will go down with time.  If the necrosis is on the larger side, it could be something else and consideration would have to be given to other etiologies.  Bad masses do not shrink with time.

 Sorry to hear about the problem.Fat necrosis may gradually decrease in size (may even liquefy and drain)  spontaneously. Other times, resection of the unhealthy tissue is necessary. If resection is undertaken it should be done in a conservative fashion avoiding removal of surrounding healthy tissue. Best wishes.