Hypertrophic scars are caused by severe acne, and result in large raised lumps of flesh which are firm and dense. These lumps of flesh are often larger in size than the pimple that caused them, and are among the hardest type of acne scarring to effectively treat. Hypertrophic scars often grow back after removal, and there may still be significant discoloration even if a hypertrophic scar is successfully removed. Steriod treatments are often used to reduce the size and appearance of hypertrophic scars, and steroids may be used either in topical form or with steroid injections. Cryosurgery has also been shown to be successful in some cases in treating and removing hypertrophic scars. Laser treatments may also reduce hypertrophic scars, though this is still a relatively new approach to hypertrophic scar treatment.