Baker Grade IV Capsular Contracture Is Correlated with an Increased Amount of Silicone Material: An Intrapatient Study

Abstract

Background:

Breast implant surgery is one of the most frequently performed procedures by plastic surgeons worldwide. However, the relationship between silicone leakage and the most common complication, capsular contracture, is far from understood. This study aimed to compare Baker grade I with Baker grade IV capsules regarding their silicone content in an intradonor setting, using two previously validated imaging techniques.

Methods:

Twenty-two donor-matched capsules from 11 patients experiencing unilateral complaints were included after bilateral explantation surgery. All capsules were examined using both stimulated Raman scattering (SRS) imaging and staining with modified oil red O (MORO). Evaluation was done visually for qualitative and semiquantitative assessment and automated for quantitative analysis.

Results:

Using both SRS and MORO techniques, silicone was found in more Baker grade IV capsules (eight of 11 and 11 of 11, respectively) than in Baker grade I capsules (three of 11 and five of 11, respectively). Baker grade IV capsules also showed significantly more silicone content compared with the Baker grade I capsules. This was true for semiquantitative assessment for both SRS and MORO techniques (P = 0.019 and P = 0.006, respectively), whereas quantitative analysis proved to be significant for MORO alone (P = 0.026 versus P = 0.248 for SRS, respectively).

Conclusions:

In this study, a significant correlation between capsule silicone content and capsular contracture is shown. An extensive and continued foreign body response to silicone particles is likely to be responsible. Considering the widespread use of silicone breast implants, these results affect many women worldwide and warrant a more focused research effort.

CLINICAL QUESTION/LEVEL OF EVIDENCE:

Risk, III.

Since its introduction, the use of silicone breast implants for reconstructive and cosmetic purposes has increased significantly; thus, breast implant surgery is one of the most frequently performed procedures by plastic surgeons worldwide.^1,2 Simultaneously, extensive research efforts and lively discussions on their safety and complications continue.^3–12 Although most of the recent attention is focused on breast implant-associated anaplastic large cell lymphoma¹³ and breast implant illness,¹⁴ the most common complications are still related to the capsule surrounding the implant. Capsule formation is a normal foreign body response, although excessive thickening and contracture are adverse reactions and may result in complaints experienced by the patient.

Prevalence estimates for capsular contracture (CC) range from 5% to 19% for breast augmentation and 19% to 25% for breast reconstruction, although numbers vary between studies.^15–18 Known risk factors include breast reconstructive surgery after breast cancer, irradiation of the breast, subglandular implant placement, postoperative hematoma, and a smooth implant surface.^19,20 Over the years, innovations have been made in implant construction to prevent significant silicone bleeding through the surrounding shell.²¹ High–cohesive silicone gels and more durable shells were introduced, in addition to novel surgical techniques. Significant gel bleed and rupture were deemed to be responsible for the high CC rates of the first- and second-generation implants.²² Together, this resulted in a reduced prevalence of CC compared with the first implant generations.^15,22,23 Despite these efforts to prevent CC altogether, the actual pathophysiologic mechanisms involved are still largely unknown.¹⁵

The Baker classification of CC uses a scale from I (no contracture) to IV (severe contracture) and is the most commonly used classification system for CC. Silicone bleeding, the leaking of small quantities of silicone gel into the surrounding tissue without an obvious tear of the implant, has previously been associated with a higher Baker score.²⁴ However, because a reliable, selective, and sensitive detection technique for silicone was missing, the extent of the relationship between silicone bleed and CC has not been directly correlated.²⁵ More precise and sensitive methods have become available to detect silicone in tissue sections. Recently, we introduced stimulated Raman scattering (SRS) microscopy as a sensitive, label-free imaging technique to detect silicone particles in tissue slides that had been hematoxylin and eosin (H&E)–stained (staining is not needed but does not interfere with the SRS measurements).²⁶ In addition, the three-phase technique, a combination of standard light microscopy, staining with modified oil red O (MORO), and transmission electron microscopy (TEM) in combination with energy dispersive X-ray microanalysis (EDX) has been proven to reliably measure silicone in tissue.²⁷

The plethora of silicone breast implants available, variety of implantation techniques, and patient factors all lead to a very diverse histology for CC.²⁸ This makes a true comparison between CC histology samples difficult. Women who develop unilateral complaints are of particular interest to include in studies about the cause of CC because their capsules offer the unique opportunity to study the differences between affected and unaffected capsules, whereas all other variables remain the same. This should enable the development of a sound pathophysiologic model of CC.²⁸

In a previous study using the same capsule collection as described in this study, we showed that Baker grade IV capsules, compared with Baker grade I capsules, were significantly thicker.²⁸ They also expressed more CD68⁺ cells, indicating an increased influx of innate immune cells (eg, macrophages), which are characteristic of foreign-body granulomatous reactions observed in reaction to fillers.^28,29 Furthermore, we observed an increase in vimentin-positive cells, indicating an increase in fibroblasts in Baker grade IV. However, an increase in the myofibroblast biomarker alpha-smooth muscle actin was not observed in Baker grade IV compared with Baker grade I CC indicating that myofibroblast formation was not directly related to contracture (unpublished data). Therefore, this study aimed to examine the relationship between Baker grade I and Baker grade IV capsules regarding silicone content, using both SRS and MORO techniques, in an intraindividual study.

PATIENTS AND METHODS

Patient and Tissue Collection

Donor-matched Baker grade I and Baker grade IV capsules from patients undergoing explantation or revision surgery between 2010 and 2014 who had developed unilateral complaints were collected (Table 1). Patients with a history of (breast) cancer and recipients of Poly Implant Prothèse implants were excluded. All patients had undergone cosmetic augmentation surgery with the submuscular (dual-plane, inframammary fold incision) method using high–cohesive gel textured implants. Although implant age and rupture were documented, unfortunately, the exact brand and type were not (Table 2). Clinical grading using the Baker classification, the collection of capsules, and the explantation surgery itself were performed by an experienced plastic surgeon (F.B.N.). Patients were included only after oral informed consent was given. These procedures were performed in accordance with the Code for Proper Secondary Use of Human Tissue as formulated by the Dutch Federation of Medical Scientific Societies.³⁰ Samples were always taken from the same area of the capsule; cranial from the inframammary incision. Surgically, 5 × 5-cm samples were taken that were subsequently processed in the laboratory. Tissue samples were fixed in 4% formaldehyde for 24 hours, then routinely processed and embedded in paraffin. Parallel paraffin sections (maximum, 20 to 40 µm apart) were used for both techniques.

Table 1.

Patient Characteristics

Characteristic	Value
No. of patients	11
Mean age ± SD, yr	46.5 ± 9.1
Mean BMI ± SD, kg/m2	25.0 ± 4.8
Mean duration of implant placement ± SD, mo	156 ± 68
Mean size of implant ± SD, cc	306 ± 10.5
Smoker	3/11
Diabetic	2/11
Tear in implant on Baker grade IV sidea	3/11
Tear in implant on Baker grade I sidea	1/11
More than one augmentation	1/11

^aTear in implant observed during explantation.

Table 2.

Capsule Grading and Quantification Results^a

	Baker Grade I				Baker Grade IV				Implant Age (mo)
	SRS		MORO		SRS		MORO
	Grade	ppm	Grade	ppm	Grade	ppm	Grade	ppm
Patient
1†	−	138	−	295	+++	1110	+	771	132
2	−	85	−	41	++	550	+++	1218	132
3	−	127	−	1286	+++	2575	+++	4112	264
4†	−	58	−	37	++	220	++	118	264
5†	+	58	++	71	+++	10,172	+++	22,434	120
6	−	63	−	4	−	16	+	21	156
7	−	580	+	297	+	498	++	1270	204
8	−	87	−	11	−	0	+++	22	155
9	+	62	+	1791	+	40	++	1505	19
10	−	92	++	150	++	105	+++	547	204
11*	+	140	+	73	−	13	+	24	180
Q1		62		37		16		24
Q3		138		297		1110		1505
Median		87		73		220		771
Mean		135.5		368.7		1390.8		2912.9
SD		150.7		598.1		3011.1		6581.2

^aSummary of silicone positivity in the capsules. Semiquantitative assessment for silicone positivity was performed visually and independently by two authors for both methods (SRS and MORO) after which a common agreement was reached. Samples were graded as containing no, a little, intermediate, or a lot of positivity (−, +, ++, or +++). Automated quantification was performed as described in the Patients and Methods section; the ratio for the positive area for silicone, relative to the total measured area of the capsule, is noted in parts per million (ppm). Tear in implant in Baker grade I side is indicated with an asterisk (*) and in Baker grade IV side with a dagger (†). For all quantified variables, the Q1 (25th percentile) and Q3 (75th percentile) interquartile range, median, mean, and SD are shown.

SRS

Histologic examination was performed on deparaffinized, formalin-fixed tissue sections (5 µm) that were stained with H&E. After staining, tissue sections were analyzed using an SRS microscopy setup as described earlier.^26,31 In short, a bright-field image was obtained of the entire slide. Next, the sample was scanned at two different wavenumbers [2905 cm⁻¹ and 2933 cm⁻¹, corresponding with the C-H stretch vibrational energies of polydimethylsiloxane (silicone) and protein, respectively], which maximized the contrast between silicone and the surrounding tissue. Then, these two SRS images were subtracted, threshold implemented, followed by processing to remove false-positive results. The processed images were overlaid with the corresponding histologic bright-field images, where the silicone was colored green. The bright-field images were recorded as tiles and retrospectively corrected for flat-field and dark-field shading.³²

MORO, TEM, and EDX

For the second method of detection of silicone, we used a combination of MORO staining, TEM, and EDX. The combination of these three techniques to detect silicone in tissue has been described previously.²⁷ Consecutive paraffin sections (4 µm) of the same tissue samples used for SRS analysis were cut, deparaffinized, and rehydrated for MORO staining, which binds specifically to the silicone polymers because of hydrophobic interactions.²⁷ Hematoxylin was subsequently used as a counterstain. Following evaluation of the stained tissue sections, several samples were selected for TEM and EDX analysis to verify the MORO staining for quality and specificity.

A selected area of the paraffin block, positive in the MORO staining, was embedded in Epon (embedding epoxy resin) for electron microscopy. Semithin and ultrathin sections were obtained with a Leica ultramicrotome. Semithin 1-μm tissue sections were stained with toluidine blue for light microscopic investigation. After further selection, 90-nm ultrathin sections were cut, also contrasted with 4% uranyl acetate/lead citrate, and examined by electron microscopy. Uncontrasted 200-nm ultrathin sections were used for EDX. The samples were studied with a Jeol (JEM-1200 EX II TEM/STEM) transmission/scanning electron microscope operating at 64 kV with EDX equipment.

Silicone Content Evaluation and Statistical Analysis

After the slides were processed, both a traditional qualitative assessment and semiquantitative scoring for positivity were carried out visually and independently by two authors for both methods. Samples were scored according to the amount of silicone and the level of silicone spread within the tissue, as no silicone, localized, intermediately spread/dispersed, or heavily dispersed (−, +, ++, or +++, respectively).

For quantitative analysis of the SRS measurements, the silicone content in the tissues was determined with the Image segmentation app in MATLAB 2020a. The ratio of the positive silicone area relative to the tissue area measured area is expressed in parts per million.

For quantitative analysis of the MORO analyzed slides, whole-slide images were acquired at 20× magnification, 0.5-µm/pixel resolution, using the Vectra Polaris scanner (Akoya Biosciences, Marlborough, MA) in bright-field mode. The density of silicone particles was analyzed using QuPath Software 0.2.3 by an automated pixel classifier using the artificial neural network model.³³ Regions (250,000 µm²) from multiple samples were used to train the classifier. In all whole-slide images, a region was created meticulously surrounding the sample. The classifier was subsequently used to analyze all samples, creating a ratio for the positive area relative to the total measured area in parts per million.

Both the semiquantitative and the quantitative results of SRS and MORO analysis were statistically evaluated using the Wilcoxon signed rank test for paired samples. A value of P < 0.05 was considered significant. For the quantified variables, descriptive statistics were calculated. All statistics were performed using SPSS (IBM SPSS Statistics for Windows, version 26.0).

RESULTS

In total, 11 patients and 22 capsules were included. Patient characteristics at baseline are shown in Table 1. The mean duration of implantation was 156 months. There were three implant tears observed at the time of explantation on the Baker grade IV side and one on the Baker grade I side (Table 2). One patient underwent the explantation procedure because of recurrent CC (patient 11). All implants were high–cohesive gel silicone implants. There were no postoperative complications, such as hematoma or infection.

The general morphology of the capsules obtained from this patient group has been described earlier.²⁸ In short, a large diversity between capsules of different patients and Baker grades I and IV was observed. Baker grade IV capsules were significantly thicker and had a higher cell density compared with Baker grade I capsules. All capsules were organized in multiple layers, with the Baker grade I capsules showing more synovial metaplasia-like layers (eight of 11 versus two of 11).

SRS Imaging Shows Increased Silicone Content in Baker Grade IV Compared with Baker Grade I Capsules

Based on visual grading, capsules obtained from nine of the 11 donors showed elevated amounts of silicone (Table 2). Silicone was detected in only three of the Baker grade I capsules, whereas silicone was detected in eight of the Baker grade IV capsules. In all but one donor, more silicone was found in the Baker grade IV capsule compared with the contralateral Baker grade I capsule. In most Baker grade IV capsules, silicone was found dispersed throughout the capsule and was seen filling vacuoles (Fig. 1), whereas in Baker grade I capsules, it was more focal or absent. Interestingly, in four of these capsules, a substantial increase in the amount of silicone was found only in the deeper sections of the capsule and was not found in the tissue directly bordering the implant (Fig. 1, below). The statistical evaluation of these semiquantitative results shows a significant difference (P = 0.019).

Fig. 1.

Overview and details of two Baker grade IV capsules, stained with H&E and examined using the SRS technique, with the implant side upward and silicone positivity overlaid with green. (Above) Capsule from patient 4, scoring ++ with a gradual dispersion throughout the capsule and with a magnification of a designated area (inset 1), showing several vacuoles near the implant side of the capsule. (Below) Capsule from patient 5, with very high silicone detection, scoring +++. Dispersion throughout and especially in the deeper layers (inset 2) and distribution at the implant side shown with two big vacuoles and multiple smaller positive spots (inset 3).

Next, the amount of silicone found was quantified and calculated in parts per million (Table 2). Again, a great variance can be seen between capsules and patients. Although the Baker grade IV capsules show comparative results in semiquantitative assessment and quantitative analysis, discrepancies exist more in the Baker grade I capsules, probably because of the lower amounts of silicone found in the tissues. Quantitative SRS analysis between Baker grade I and Baker grade IV capsules was not able to reject the null hypothesis (P = 0.248). However, the relative amount of silicone in the tissue showed an inconclusive trend, with a higher mean level for Baker grade IV (1475 ppm) in comparison with Baker grade I (135 ppm).

MORO, TEM, and EDX Show Increased Silicone Content in Baker Grade IV Compared with Baker Grade I Capsules

Silicone particles were detected with MORO staining in five of 11 Baker grade I capsules, whereas particles were found in all Baker grade IV capsules (Table 2 and Fig. 2). In line with the SRS-analyzed tissue sections, there was a clear increase in the number of particles found in Baker grade IV capsules in comparison with Baker grade I capsules. Similar to SRS, MORO staining resulted in five of the Baker grade IV capsules showing a lot of positivity throughout the entire capsule (compare Fig. 2, left, Baker grade I, with Fig. 2, center, Baker grade IV). As with the SRS analysis, there was a dispersed pattern of positivity with a tendency to fill vacuoles or positivity in the general area of the vacuoles for most capsules (Fig. 2). Based on the light microscopic findings, the Baker grade I capsule of patient 11 and the Baker grade IV capsule of patient 5 were selected for TEM/EDX and to confirm accurate staining of silicone for all samples (Fig. 3). The Baker grade I capsule from patient 11 shows only small focal spots of positive staining. However, TEM/EDX did confirm that these small granules contain a lot of silicon-containing molecules, measuring 64,078 silicon counts (Fig. 3). [See Figure, Supplemental Digital Content 1, which shows (left) an output graph of the EDX measurement performed on the Baker grade I capsule from patient 11, with the focal spot showing 64,078 silicon counts, http://links.lww.com/PRS/G267.] The Baker grade IV capsule of patient 5 shows a lot of positivity in the MORO staining (+++) and an abundant number of vacuoles. These were confirmed to contain very high counts of silicon, as the single vacuole in measuring point 014 measured 718,378 silicon counts (Fig. 3). [See Figure, Supplemental Digital Content 1, which shows, (right) an output graph of the EDX measurement performed on the Baker IV capsule from patient 5, with the focal spot showing 718,378 silicon counts, http://links.lww.com/PRS/G267.] The statistical evaluation of these semiquantitative results shows a significant difference between Baker grade I and Baker grade IV capsules (P = 0.006).

Fig. 2.

Overview and details of capsules Baker grade I and IV examined with the MORO technique, with the implant side upward, and silicone positivity seen as a red dye. (Left) Baker grade I capsule from patient 11, scoring +. A small focal spot can be seen centrally in the image (arrow) at the implant side, whereas a larger focal spot is observed on the patient side of the capsule (arrowhead). (Center) Baker grade IV capsule from patient 5, scoring +++ with a gradual dispersion throughout the capsule (right, inset 1), dispersed positivity, and large vacuoles near the implant side of the capsule and large amounts of smaller granules in the deeper layers of the capsule (right, inset 2).

Fig. 3.

Overview and details of capsules from Baker grade I and IV capsules examined with TEM in combination with EDX. (Left) TEM micrograph of the EDX measurement performed on the Baker grade I capsule from patient 11; inset 1 shows focal measurement spot indicated with an asterisk. The measured point showed 64,078 silicone counts. (Right) TEM micrograph of the EDX measurement performed on the Baker grade IV capsule from patient 5. The vacuole containing point 014 was measured to show 718,378 silicone counts. Original microscopic magnifications figure left and right: 5000 and 12,000, respectively. The graphs from both measurements are included in Figure, Supplemental Digital Content 1, http://links.lww.com/PRS/G267.

The quantification of these slides is in line with the other results in that they display a large variance between capsules and patients. The same incongruent pattern between semiquantitative assessment and quantitative assessment can be seen here as well, again, especially for the Baker grade I capsules. However, again there is a significant difference between Baker grade I and Baker grade IV capsules (P = 0.026). As in the SRS quantification, a higher mean parts per million was seen here for Baker grade IV in comparison with Baker grade I (2913 ppm versus 369 ppm, respectively).

See Table 2 for descriptive statistics of nonparametric variables. No significant differences were found between the SRS and MORO techniques.

DISCUSSION

The multitude of articles published about CC clearly shows that it is a multifaceted process. The aim of this study, therefore, was to correlate a CC severity score (the Baker score) with silicone found in the capsule surrounding the breast implant. In current studies describing modern breast implants, silicone release and its effects are missing. By using material from patients with unilateral complaints, donor variation can be eliminated comparing Baker grade I and Baker grade IV CC. Here, we show that by using this concept, a strong correlation is found between CC and the amount of silicone found in the capsule, which was proven to be significantly different by two independent techniques (SRS and MORO). These results suggest that the increased deposition of silicone particles in the capsule is responsible for the extensive fibrotic capsule formation and contraction found in CC.

In asymptomatic capsule formation, macrophages and fibroblasts (among other cells) provide a foreign-body response in which organized fibrous tissue layers form an initial capsule.¹⁵ In these thin and supple (Baker grade I) capsules, we previously demonstrated the presence of a synovial metaplasia-like inner layer, with a significantly lower presence in the Baker grade IV capsules.²⁸ This inner layer may serve as a protective layer, allowing the body to return to a resting state.³⁴ In time, and not in all patients, a secondary local process starts in which CC occurs. The amount of gel bleeding has been described to correlate with CC, indicative that the amount of silicone presented to the body plays a significant role.³⁵ In this collection, patients 1, 4, and 5 had an intraoperative tear on the Baker grade IV side and patient 11 had an intraoperative tear on the Baker grade I side (Table 2). Although the Baker grade IV side of patient 5 scored high grades and silicone counts in both SRS and MORO analysis, this was not uniformly seen for patients 1 and 4. The Baker grade I capsule of patient 11 was positive for silicone, but so were other capsules in the Baker grade I collection without torn implants. Therefore, the presence of a tear cannot completely explain our results. However, imaging studies have shown that patients often have torn implants before CC exists, suggesting the silicone leakage from the tear might be responsible for the CC reaction.³⁶ Also, silicone has been shown to sweat or bleed from the implants and has been shown to contribute to capsular contracture.³⁵ Patient 9 was scored a + in MORO in Baker grade I and a ++ in Baker grade IV; the grade in SRS was the same. Objectified counts differed for these variables. As with all clinical studies, our capsule study showed a great variance (probably attributable to patient variation and the different techniques used) between some samples, so some comparisons between individual capsules might not always be in line with the results of the entire collection. CC is associated with increased numbers of cells commonly found in the foreign-body reaction such as T-cells, macrophages, fibroblasts, giant cells, and contractile myofibroblasts.^15,37–43 Considered together, this indicates that a secondary foreign-body reaction seems to be responsible for CC. Variations in implant placement, pressure during day-to-day activities, and quality (shell integrity) could correlate to a variation in silicone leakage into the tissue and therefore capsule formation and contracture and could explain unilateral complaints. It is notable that whereas most Baker grade IV capsules show a generalized spread of silicone throughout, in some cases, silicone was located primarily in the deeper regions of the capsule (away from the implant). Reasons for this are still unknown and require further investigation.

Modern techniques aid us in easy and automated quantification for both techniques used in this study. Although “hard numbers” aid in a clear message, visual assessment is essential to obtain a more thorough analysis of the location of silicone and the characteristics of the tissue, which is why in this study both approaches were performed. A traditional semiquantitative assessment of images performed by a pathologist involves much more than just the amount of positivity in a staining. A large single positive area will cause a high spike in automated measuring programs, whereas an expert will consider the total distribution rather than just localized presence in the sample. The abundance of cells and dispersed silicone pattern in some of the Baker grade IV capsules indicates a more thorough response by the body than just a large uniform amount of silicone would.

The different methods used to investigate silicone amounts in tissue sections may result in diverse results. The fluidity of silicone can influence the detection of silicone content in capsules in multiple ways. Although the deparaffinization step in tissue section preparation does not seem to influence the amount of silicone found, tissue preparation before that step might cause the silicone to leak out of the sample.²⁶ Silicone concentration in the capsule might be far from homogeneous, so the amount of silicone detected can be subject to sampling error. This can explain the differences between the sample sets used for SRS and MORO because the histologic slides were a few microns apart. As the surface area of a capsule is more than 1000 times larger than a regular histologic slide, it would be extremely time consuming to analyze the entire capsule. However, in future studies, it would be advisable to take a limited number of biopsy specimens from random sites within the capsule.

The Baker classification used in our study to distinguish between affected and unaffected capsules is subjective and considered unreliable as a diagnostic tool.⁴⁴ It is, however, the most commonly and easily used tool in normal practice and does indicate complaints. Moreover, although used as a measure for capsular contracture, actual contracture is not measured. It is more indicative of capsule thickening and hardening. Other tools, such as high-definition ultrasound and magnetic resonance imaging, can be considered to assess implant folds and deformation as a measure of contracture.^45,46

The mean age of the implants (and thus the capsules) is 156 months. However, age did not have a significant influence on the amount of silicone found in the capsules in this study (Table 2). For this group of patients, no advice on regular revision surgery existed. Currently, revision surgery is advised every 10 to 15 years, comparable to the timespan our patients had the implants.⁴⁷

Although this study shows a significant correlation between silicone content and CC, these results do not necessarily mean that the implants in women with Baker grade I capsules do not lose silicone to the tissue over time. Future research could also include investigating the loss of silicone out of the tissue during the different processing steps, as we saw many empty vacuoles in our samples. Capsules obtained from saline implants exhibit comparable or higher CC rates compared with full silicone implants.^19,20 However, because only the shell is made from silicone, these capsules are still interesting.⁴⁸ In a study using plasma emission spectroscopy, silicone was found in these capsules, so further analysis with the visual histologic properties used in this study would be of interest in further understanding this adverse effect.⁴⁹ Finally, confirmation in larger sample sizes seems a logical step in addition to determining differences between implants in terms of silicone loss.

There used to be a time in which plastic surgeons told patients that silicone implants did not need to be renewed or removed; however, this has been changing over the years.⁴⁷ If we consider silicone to be an essential factor in the development of CC, the role of silicone as the dominant ingredient of breast implants should be questioned. At the very least, new implants should deteriorate and leak silicone as little as possible.

CONCLUSIONS

In this intraindividual Baker grade I versus Baker grade IV study, we show a significant correlation between capsule silicone content and capsular contracture, with Baker grade IV tissue containing more silicone than Baker grade I tissue. An extensive and continued foreign body response to silicone particles is probably responsible. Considering the widespread use of silicone in breast implants, these results are relevant to many women worldwide.

DISCLOSURE

The authors have no financial interest to declare concerning the content of this article.

ACKNOWLEDGMENTS

This work was supported by the Horizon 2020 Framework Programme (grant/award no. 654148), Nederlandse Organisatie voor Wetenschappelijk Onderzoek (grant/award no. 053.21.112), and Health~Holland (grant/award no. TKI 16.01). The authors thank L. van den Broek (Amsterdam UMC; location, VUMC), E. de Miguel (Amsterdam UMC; location, VUMC), and Ine van Raaij (Radboud University Medical Center) for technical assistance; J. F. de Boer (LaserlaB, Vrije Universiteit Amsterdam) and H. A. Leslie (Department of Environment and Health, Vrije Universiteit Amsterdam) for critical feedback on the SRS results; and B. Lissenberg-Witte (Amsterdam UMC; location, VUMC) for assistance with the statistical analysis.