Direct injection of foreign material, such as liquid paraffin and silicone, into thebreast can induce a foreign body granulomatous reaction and fibrosis, resulting inhard, nodular breast masses and architectural distortion that can mimic neoplasm. Conventional methods, including physical examination, mammography, andultrasonography are of little use to differentiate between foreign body-inducedmastopathy and breast cancer. In patients with foreign body injection such as breastaugmentation, dynamic contrast enhanced MR imaging is an excellent imagingmodality. Here, the authors report the MR imaging and pathological findings ofductal carcinoma in situ (DCIS) with multicystic changes in a 41-year-old womanwith a previous history of interstitial mammoplasty by paraffin injection.