Objective: The purpose of this study was to determine the mammographic and sonographic findings of injuries of the breast caused by seat belts in automobile accidents. The imaging findings of such injuries must be differentiated from those of carcinoma, so that inappropriate treatment is avoided.
Materials and methods: Five patients who had breast injuries caused by seat belts with shoulder restraints between 1988 and 1993 and who underwent mammography were included in this study. Four of these women had imaging studies done in our department, and one was examined elsewhere. The initial mammograms for four patients were obtained 1-2 months after trauma to the breast. For the fifth patient, the initial study was obtained 13 months after injury. For all women, follow-up examinations were performed from 3 months to 4 years after injury. Two patients also underwent sonography of the breast during the course of their evaluation.
Results: At 1-2 months after breast injury caused by a seat belt, mammograms showed thin-walled fat-density cysts in a linear distribution and, in less dense breasts, an associated 2-3-cm band of increased density. The band of increased density was not seen in more dense breasts. These findings correlated with the line of contusion across the breast and resultant fat necrosis, which ultimately led to the formation of lipid cysts. By 3-4 months after the injury, the lipid cysts and contusion were less apparent, and a line of fibrosis had developed. On sonography, the lipid cysts were smoothly marginated; such cysts may be either anechoic or hypoechoic. Parenchymal calcification may develop 3.5-4 years after such an injury.
Conclusion: Mammograms in women with breast injuries caused by seat belts show areas of contusion, lipid cysts, and parenchymal calcifications occurring in a bandlike distribution corresponding to the path of the seat belt shoulder restraint across the chest. Lipid cysts are seen sonographically as smoothly marginated anechoic or hypoechoic nodules.