The Palpable Nodule after Autologous Fat Grafting: Distinguishing Benign versus Malignant Lesions in Breast Reconstruction

Background: Nodule formation after autologous fat grafting to the breast is the most common complication. In the reconstructive population, this generates significant patient anxiety and presents a diagnostic challenge. The authors characterized palpable nodule occurrence after autologous fat grafting in breast reconstruction and compared benign versus malignant nodule characteristics. Methods: Chart review of the senior author's experience with breast fat grafting was performed. Data extracted included demographics, intraoperative details, nodule data, radiographic characteristics, and biopsy results. Logistic regression identified risk factors for nodule formation. Unpaired t tests and Fisher exact tests compared characteristics of benign versus malignant nodules. Results: In total, 775 breasts were identified that underwent 1158 fat grafting procedures, of which 67 (8.6 percent) developed palpable nodules. Sonographic characterization of nodules included presumed fat necrosis (38.2 percent), benign lesions (27.6 percent), presumed oil cysts (17.1 percent), indeterminate (8.9 percent), and concerning for malignancy (8.1 percent). Lesions concerning for malignancy were more often irregular (10.0 percent versus 0 to 2.9 percent of benign nodules) and more often larger than 0.8 cm in greatest dimension (80 percent versus 42.9 to 61.8 percent of benign nodules). Six patients developed a palpable local recurrence. Malignant nodules tended to be larger (1.45 cm versus 0.70 cm; p = 0.03), were more often vascular (50 percent versus 3.8 percent; p = 0.03), and tended to occur later (17.5 months versus 10.0 months; p = 0.60). Benign nodules occurred in the setting of larger fat graft volumes (64.2 cc versus 40.0 cc; p = 0.008). Conclusion: This study provides the first comparison of radiographic and clinical characteristics between benign and malignant palpable nodules after autologous fat grafting in breast reconstruction. CLINICAL QUESTION/LEVEL OE EVIDENCE: Risk, III.