Background: In prepectoral breast reconstruction (PPBR) the acellular dermal matrix (ADM)'s integration capacity into the tissue is known. The aim of this study was to analyze the effect of the ADM on development and composition of the peri-implant breast capsule in a dynamic setting of breast tissue expansion during two-stage prepectoral breast reconstruction.Methods: This is a prospective single-center study in which 50 patients who underwent mastectomy and breast reconstruction with prepectoral tissue expander and Braxon ADM (group A) and submuscular tissue expander (group B) were enrolled. One-year post implantation hematoxylin & eosin (H&E) staining and immunohistochemistry analyses were done on capsule tissue samples.Results: The analysis conducted on H&E-stained samples showed a significant reduction of cellular density and a decrease of the cellular infiltration in capsules of ADM-covered expanders compared with naked expander capsules (P < 0.05). The immunohistochemical analyses showed that group A capsules presented significantly less M1 CD68+ macrophages (P < 0.05), lower alfa-SMA expression levels, and a lower number of myofibroblasts (P < 0.05) compared with group B capsules. Presence of lymphatic vessels was minimally detected in both groups.Conclusions: The ADM presence around the prepectoral tissue expander influences the development of the peri-implant capsule, causing a significant reduction of the number of cells and inflammatory infiltrate, especially M1 macrophages and myofibroblasts. The ADM Braxon is therefore effective in creating a noninflamed capsule around the implant and in dynamic tissue conditions, and such an environment is maintained in time.
