What causes fat grafts to become oil cysts or encapsulate and calcify?

There is a series of processes that need to happen correctly for a successful fat grafting.  It starts with the harvest (the obtaining of the fat) thru the cleaning/separation of the fat from the oil and fluid thru the injection/grafting process.Any issues during any of the steps can lead to the fat not incorporating or taking and then eventually lead to fatty cysts, hard lump and or calcification with time.Hope that helps.

fat can clump together and die becomming oil cysts which represents collections of dead fat cells; these cells will become calcified and eventually be absorbed by your body. This process may take several years so be patient. The key to avoiding this complication is to graft fat cells in small aliquots, for example in 0.5cc to 1.0cc 

Calcification or oil cysts are the result of improperly prepared or injected fat. If the fat is too roughly harvested or purified, it may not survive and will form calcifications as a result of the fat cell dying. If too much fat is injected  in one location at a time inject of being dispersed, then the fat dies and becomes an oil cyst.Technique is always very important. 

Patients need to understand that fat grafting is an unpredictable process and that when the fat doesn't survive, it can turn into hard scar, cysts, and even infection. Somehow, patients don't want to hear this and they would rather believe that all will be perfect when they have fat grafting. Simply not the case.In order to survive, the fat cells need to have blood vessels re-hooked up into them and this doesn't always happen regardless of all the maneuvers of the surgeon.