 It is a common misconception that the lump is largely scar tissue, as injection site hypertrophy is much rarer and milder with injections of other hormones and medications which lack the specific ability of insulin to stimulate adipose hypertrophy.In a sense, the "opposite" of injection site lipohypertrophy is injection site lipoatrophy, in which the subcutaneous fat around an injected area "melts away" over a few weeks or months, leaving unsightly, well-demarcated depressions in the skin.The mechanism of this local lipoatrophy is not understood and may involve autoimmunity or local inflammation.