The Histological Composition of Capsular Contracture Focussed on the Inner Layer of the Capsule: An Intra-Donor Baker-I Versus Baker-IV Comparison

Abstract

Background: Capsular contracture remains one of the major complications after breast implantation surgery. The extent of capsular contraction is scored using the Baker scale. The aim of this study was to compare intra-individual Baker-I with Baker-IV capsules, and in particular the prevalence and histological properties of the inner capsule layer.

Methods: Twenty capsules from ten patients were included after bilateral explantation surgery due to unilateral capsular contracture (Baker-IV) after cosmetic augmentation with textured implants. All capsules underwent (immune-)histochemical analysis: haematoxylin-eosin (morphology), CD68 (macrophages), cytokeratin (epithelial cells) and vimentin (fibroblasts), and were visually scored for cell density and the presence of an inner layer and measured for thickness.

Results: Baker-IV (n = 10) capsules were significantly thicker compared to Baker-I (n = 10) capsules (P = 0.004). An inner layer was present in 8 Baker-I capsules. All Baker-I capsules were vimentin and CD68-positive and cytokeratin-negative. Positive vimentin was seen throughout the inner layer, and CD-68 staining was observed adjacent to the intermediate capsule layer. In contrast, only 2 Baker-IV capsules had an inner layer, of which only 1 showed the same profile as Baker-I capsules (P = 0.016). No cytokeratin positivity was seen in any capsule. In Baker-IV capsules, outer layers showed more positivity for both vimentin and CD68.

Conclusion: The inner layer is morphologically consistent with synovial metaplasia and is more prevalent in healthy, uncontracted Baker-I capsules. This inverse relation between the presence of the inner layer and higher Baker classification or pathological contracture could indicate a protective role of the inner layer against capsular contracture formation.

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Keywords: Breast augmentation; Breast reconstruction; Capsular contracture; Histology; Immunohistology; Synovial metaplasia.

Fig. 1

Intra-donor differences in Baker-I and Baker-IV capsular thickness. Average of 5 different measurements within a tissue section is shown for each capsule. Each line represents one donor with a Baker-I and a Baker-IV capsule. Thickness is shown in micrometre (µm)

Fig. 2

Capsule thickness measurement and layers. Representative photograph of Baker-IV capsule is shown with a inner layer, b intermediate layer—note extracellular matrix is aligned in line with the implant and c outer layer—note extracellular matrix is aligned perpendicular with the implant. The 5 thickness measurements used in Fig. 1 are indicated with green bars

Fig. 3

(Immuno-)histochemical staining results of a representative Baker-I and Baker-IV capsule from the same donor. Shown are × 10 and × 40 magnifications