Histological Remodeling of Irradiated Postmastectomy Breast Tissue After Autologous Fat Grafting: A Prospective Paired Tru-Cut Biopsy Study

Background/Objectives: Radiotherapy following mastectomy induces persistent structural alterations in the chest wall, including fibrosis, extracellular matrix disorganization, and vascular changes that compromise reconstructive outcomes. Although autologous fat grafting is widely used to improve tissue quality in irradiated breasts, direct human histological evidence remains limited. The aim of this prospective pilot study was to evaluate intra-patient histological remodeling in irradiated postmastectomy breast tissue before and 4 months after autologous fat grafting using paired core needle biopsies. This study should be considered a hypothesis-generating histological pilot study. Methods: Five female patients with prior mastectomy and adjuvant radiotherapy underwent Tru-Cut core needle biopsy of irradiated chest wall tissue before lipofilling and at approximately four months (range between 3 and 12 months) post-procedure. Specimens were processed using formalin fixation, paraffin embedding, and hematoxylin and eosin staining. Histological assessment focused on collagen density, stromal organization, vascular structures, inflammatory infiltrate, and adipocyte integration. Comparative intra-patient analysis was performed descriptively. Results: Baseline biopsies demonstrated consistent post-radiation alterations, including collagen compaction, stromal disorganization, perivascular fibrosis, and variable inflammatory infiltrate. Post-lipofilling specimens showed heterogeneous remodeling characterized by focal collagen fiber insertion between adipocytes, areas of immature connective tissue formation, and variable preservation of adipose architecture. The extent and pattern of remodeling differed among patients. Inflammatory activity decreased or remained mild in most cases. Conclusions: Autologous fat grafting in irradiated postmastectomy tissue is associated with measurable histological remodeling. Structural adaptation appears heterogeneous and patient-specific, suggesting a dynamic multi-stage process rather than uniform regeneration. Further studies incorporating quantitative and molecular analyses are required to clarify the mechanisms underlying these changes.