Breast Implant Microbiome Differs By Incision Site But Not By Implant Plane: An Analysis of 389 Explanted Implants.

BACKGROUND: Subglandular implant placement and periareolar incisions have historically been associated with higher capsular contracture rates than subpectoral placement and inframammary fold (IMF) incisions. These differences have often been attributed to greater implant exposure to endogenous breast microbiota. OBJECTIVES: To compare microbiome diversity and composition on explanted breast implants between subpectoral and subglandular planes, and among IMF, periareolar, and transaxillary incisions, and assess whether greater parenchymal exposure is associated with persistent microbiome differences. METHODS: We analyzed explanted implants from patients undergoing revisional surgery after breast augmentation using 16S rRNA gene amplicon sequencing. We compared alpha- and beta diversity and differential abundance of the dominant genera, adjusting for capsular contracture, implantation time, surface texture, smoking status, and within-patient clustering. RESULTS: We analyzed 389 implants from 219 patients, of which 336 (86%) were subpectoral and 53 (14%) were subglandular. We did not detect differences between plane groups in alpha diversity (Shannon 1.7 vs 1.7, padj=0.62), community composition (PERMANOVA padj=0.46), or differential relative abundance of the dominant genera. In contrast, implants placed with a periareolar incision (n=45) showed higher richness and a distinct composition compared with the IMF group (n=308, Bray-Curtis padj=0.004), with no significant difference between IMF and transaxillary access (n=36, padj=0.12). CONCLUSIONS: We did not detect differences in relative microbiome diversity, community composition, or differential relative abundance of dominant genera between implant planes. In contrast, incision site was associated with consistent microbiome differences, suggesting that implantation route may influence the long-term implant microbiome.