Silicone granuloma (painful nodes) is the most common complication of liquid injectable silicone. Granuloma is a medical and pathological term used to describe the formation of a mass of immune cells, inflammatory cells and scar tissue that forms when the immune system attempts to wall off substances that perceives as foreign but is unable to eliminate. When silicone is injected into the buttocks or any other area of the body, a similar response occurs. The reaction of liquid silicone injected to the buttocks vary considerably and depends on the amount and type of silicone injected. There are two general clinical presentations. In the first one, the patient presents painful multicystic lumps on the buttock area. This can occur in the early years or as long as 10 -15 years after the injection.the second presentation is characterized by skin inflammation and breakdown as the silicone migrates close to the skin. Also, these lesions manifest as recurrent infections with pain and hardening of the buttocks.
The exact mechanism is not fully understood but multiple theories exits. It is known that silicone is not completely biologically inert. Silicone undergoes a biological oxidation to silica. This product is incorporated in some cells called reticular endothelial cells. It is speculated that this oxidation into silica sets the stage for the painful granulomas manifested.