Florid inflammatory reaction after fat grafting into an irradiated DIEP-reconstructed breast mimicking cancer recurrence.

Autologous fat grafting (AFG) is widely used to refine contour and volume following breast reconstruction. However, its use in previously irradiated fields carries a higher risk of complications and poses diagnostic challenges in excluding locoregional recurrence. We report an unusual early inflammatory reaction following AFG into an irradiated Deep Inferior Epigastric Perforator flap-reconstructed breast, characterized by florid indurated, erythematous nodules within the fat-grafted native chest wall skin that clinically mimicked cancer recurrence. The lesions resolved with conservative management, and the patient uneventfully underwent further stages of lipofilling for symmetry. We postulate that the reaction represents an exaggerated inflammatory response to injected fat within a radiation-damaged microenvironment, a phenomenon not previously described in native irradiated breast skin following AFG. This case highlights an unreported complication of AFG and the diagnostic challenges it may pose. Clinicians should maintain a high index of suspicion and biopsy and image any suspicious lesion in these patients.