Differentiating Fat Necrosis from Recurrent Malignancy in Fat-Grafted Breasts

BACKGROUND: In breast reconstruction with autologous fat grafting, concerns persist about the ability to differentiate palpable masses representing fat necrosis from recurrent cancer. The authors' objective was to develop standardized imaging classifications to distinguish benign from malignant lesions after fat grafting. METHODS: A database of 286 breast reconstruction patients undergoing fat grafting from 2006 to 2011 was retrospectively reviewed to identify patients with imaging of clinically palpable masses. All images were reviewed independently by a radiologist blinded to prior results. Lesions were classified, using the American College of Radiology Breast Imaging Reporting and Data System ultrasound lexicon, as follows: A, solid mass, hypoechoic; B, solid mass, isoechoic; C, solid mass, hyperechoic; D, solid mass, complex echogenicity; E, anechoic mass with posterior acoustic enhancement; F, cystic mass with internal echoes; and G, negative. Evolutions in lesions on follow-up ultrasound were recorded. Images were correlated with histopathologic results. RESULTS: On ultrasound, 66 lesions were visualized in 37 patients with palpable masses. Twenty-two lesions (33 percent) were Breast Imaging Reporting and Data System category 4 lesions; biopsies were performed on all of them. Histopathologic results revealed that 85.7 percent (six of seven) with classification D and 100 percent with classifications A, B, C, E, F, and G were fat necrosis. The one malignant lesion (classification D) exhibited vascularity and angular margins on ultrasound and was not in the location of fat injection. Negative predictive value of avascularity and circumscribed margins for malignancy was 100 percent. Follow-up ultrasound of 29 lesions at a median of 6.5 months revealed that no masses increased in size or developed vascularity. CONCLUSION: Ultrasound analysis, with a standardized classification system, is reliable at differentiating benign from malignant lesions after fat grafting in breast reconstruction.