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Magnetic resonance imaging characteristics of paraffinomas and siliconomas after mammoplasty.

BACKGROUND AND PURPOSE
Breast paraffinomas and siliconomas are granulomas caused by tissue reaction to paraffin oil and silicone injection after mammoplasty. These granulomas usually present as multiple hard masses that mimic breast cancer. Mammography and sonography have only a limited role in differentiating these masses. Magnetic resonance (MR) imaging findings of these granulomas have rarely been reported. This study evaluated the MR imaging manifestations of these granulomas.


MATERIALS AND METHODS
MR imaging, mammography, and sonography were used to examine 58 breasts in 29 women with breast lumps who had undergone mammoplasty with injections of paraffin oil (n = 8) or liquid silicone (n = 50). The protocol included T1-weighted images (T1WI), fat-suppressed (FS) T2WI, post-contrast FS three-dimensional fast dynamic sequences, and FS T1WI.


RESULTS
Deep structures of the 58 breasts could not be clearly evaluated by sonography or mammography. Two types of MR imaging characteristics were identified: type I lesions were hypointense on T2WI and type II lesions had mixed hypointense and hyperintense components on T2WI. Both showed intermediate intensity on T1WI and revealed no enhancement on post-contrast dynamic sequences and FS T1WI. Type II lesions were seen only in siliconomas. Mastectomy was performed on seven breasts and paraffinomas or siliconomas were confirmed by pathology. When correlating MR images with pathology, hypointense lesions on T2WI in both type I and II lesions were foreign body granulomas with fibrosis and calcification. Hyperintense lesions on T2WI in type II were liquid silicone. A case of infiltrating ductal carcinoma was found in one breast in which MR imaging was successful in identifying the strongly enhanced solitary tumor from a background of type I lesions of paraffinomas preoperatively. Of the 51 breasts that did not receive surgery, no breast cancers were detected clinically or by follow-up imaging after a median of 27 months (19-54 mo).


CONCLUSIONS
Breast paraffinomas and siliconomas after mammoplasty have specific MR findings that are distinct from those of breast cancers. MR imaging is superior to sonography and mammography in the evaluation of breast paraffinomas and siliconomas.