Silicone induced granuloma of breast implant capsule (SIGBIC) main aspects in MRI - case series
Grasiela Costa Silva Amazonas Oncology Control Center Foundation
https://orcid.org/0000-0002-9906-4711
Rosimara Eva Ferreira Camelo Imagens Médicas de Brasília - IMEB, Brasília,
DF, Brazil
https://orcid.org/0009-0009-0942-1067
Filipe Ramos Barra Imagens Médicas de Brasília - IMEB, Brasília, DF, Brazil
https://orcid.org/0000-0002-4404-0413
ABSTRACT
The silicone-induced granuloma of the breast implant capsule (SIGBIC) is a rare and benign complication resulting from breast silicone implant placement. Since these surgeries are common, complications caused by silicone implants are becoming more frequent and are usually detected through breast magnetic resonance imaging (MRI). Given the increasing frequency of SIGBIC, the key MRI findings should be described and exemplified. This article presents a series of 14 cases identified at a private diagnostic imaging clinic in Brasília, DF, Brazil, from 2018 to 2024. Therefore, this condition must be well-known and accurately reported by radiologists.
Key words:breast implant, silicone granuloma, breast granuloma, Breast Magnetic Resonance Imaging, breast imaging.
INTRODUCTION
Surgeries for breast implant placement are commonly performed for aesthetic or reconstructive purposes1. Due to their frequency, especially in Brazil, complications related to silicone breast implants have been reported. These complications may be associated with the procedure itself, implant integrity, and/or autoimmune response2,3. Recently, silicone-induced granuloma of the breast implant capsule (SIGBIC) has been recognized as a rare and benign complication related to the phenomenon of "gel bleeding" or "silicone bleeding" from an intact implant3,4. This condition is typically detected by breast magnetic resonance imaging (MRI), but its findings can resemble those of breast malignancy, such as Breast Implant-Associated Large Cell Lymphoma (BIA-ALCL)5,6,7. Given the relevance of SIGBIC and its imaging similarity with BIA-ALCL, a proper differentiation must be made during breast MRI interpretation to avoid unnecessary biopsies. Since only a few cases have been published in the literature, the objective of this study is to present the most common imaging findings of SIGBIC in MRIs performed at our service from 2018 to 2024, as well as to provide examples and guidance to radiologists for accurate diagnosis.
CASES REPORT
To exemplify the main imaging characteristics of SIGBIC in breast MRI, the radiologic reports and images of breast MRIs from patients with this diagnosis were reviewed at a private diagnostic imaging clinic in Brasília, DF, Brazil, over a period of six years (2018 to 2024). During this period, 12.622 breast MRI exams were performed, of which 3,406 showed silicone implants. The terms “MRI,” “granuloma,” and “silicone” were searched in the clinic's database. A total of 32 cases were identified. Cases with granulomas outside the fibrous capsule were excluded. Fourteen cases of SIGBIC were identified, with an average patient age of 60 years (range: 39 to 82 years). All subjects were female with intact silicone implants, and the average time since implant placement was 9.6 years (range: 1 to 30 years). In these cases, breast MRI was recommended to assess the integrity of the breast implants or to evaluate the response to neoadjuvant therapy. No clinical signs or symptoms were assessed. Four radiologists with around 10 years of experience analyzed the exams.
All examinations were performed on high-field equipment (1.5T) and high-performance gradients, with the following pulse sequences: axial FSE T1 and axial FSE T2, with and without fat suppression, axial DWI (b=750 s/mm2 and b=1500 s/mm2), 3D VIBRANT sagittal pre- and post-contrast (dynamic study) and isotropic axial T1 with post-contrast fat suppression. The contrast medium used was gadodiamide (Ominiscan®), at a dose of 0,1 ml/kg.
The hypothesis for SIGBIC diagnosis was based on imaging findings, which included the presence of a nodule between the elastomer and the fibrous capsule, exhibiting a heterogeneous and/or hyperintense signal on T2-weighted sequences, progressive contrast enhancement and hypointensity on T1-weighted sequences, as demonstrated in Figures 1 to 4. In addition to these findings, two patients showed a small amount of pericapsular collection, along with thickening and enhancement of the fibrous silicone capsule. Only one patient presented both a small pericapsular collection and focal thickening of the fibrous capsule simultaneously, as shown in Figures 5 and 6. Interestingly, the nodule and focal thickening had similar imaging characteristics, which supported the SIGBIC diagnosis. None of the cases showed capsular contracture or intra- or extracapsular rupture.
Biopsy was not indicated, as SIGBIC is an indolent entity, and no other plausible diagnostic hypothesis was identified in the selected cases. Imaging follow-up was recommended.
DISCUSSION
Breast implant placement can lead to complications that may be associated with the procedure itself, implant integrity, and/or an autoimmune response2. After surgery, the breast forms a fibrous capsule around the implant, which contains macrophages, lymphocytes, and fibroblasts. This capsule isolates the silicone contents within the intracapsular space, creating a poorly vascularized layer3.
All breast implants may experience increased fragility over time or due to trauma or temperature changes, leading to biodegradation of the implant shell, regardless of type or brand1,3. This phenomenon allows microscopic silicone particles to leak from intact implants into the intracapsular space. The contact of these particles with the fibrous capsule triggers an autoimmune response, which promotes the formation of intracapsular granulomas, known as SIGBIC1,8.
SIGBIC is an indolent pathology; however, since it is an inflammation-induced condition, it can present with nonspecific symptoms, some of which have been reported by patients with breast implant illness (BII)1. For this reason, it is believed that "silicone bleeding" could be a common event in both indolent and more aggressive diseases, such as breast implant-associated anaplastic large cell lymphoma (BIA-ALCL)6,9.
Breast MRI is the imaging method of choice for evaluating breast implants and is a valuable tool for properly identifying SIGBIC. However, its imaging enhancement patterns can often mimic malignancy, especially when there is synchronous seroma. Nevertheless, the imaging features of breast MRI are essential for correctly differentiating these entities5,10.
This study presents a case series of SIGBIC identified using two of the proposed diagnostic criteria found in the literature. Recent studies highlight three major MRI imaging features: the presence of a heterogeneous hypersignal intracapsular mass on T2-weighted sequences, showing late enhancement on dynamic sequences; and the black drop signal, characterized by a hyposignal focus between the mass and the silicone implant on T1 sequences3,10. Fluid collection without enhancement and capsular contracture may also be associated3. In this regard, correct SIGBIC identification on breast MRI is not feasible without the intravenous administration of a paramagnetic contrast medium (gadolinium)2.
Although reports strongly suggest that the black drop signal is a consistent imaging finding in breast MRI, none of the included cases presented it. It is hypothesized that the protocol and/or the quality of the MRI device used may have influenced the visualization of this finding. Other factors, such as variations in silicone implant age, may also be considered.
Due to its indolent nature and distinctive imaging appearance, SIGBIC was the primary diagnostic hypothesis in all cases. Periodic breast MRI follow-up was recommended, and after follow-up, the SIGBIC hypothesis was maintained.
The main MRI findings of BIA-ALCL are similar, but an intracapsular collection is typically associated6. None of the selected cases presented a significant intracapsular collection; therefore, this diagnosis was not considered.
Thus, the relevance of SIGBIC in the current clinical scenario, along with its underdiagnosed frequency in breast MRI routine, makes its correct recognition and diagnosis essential. This should be done while keeping ALCL in mind as a differential diagnosis, given the potential physiopathological similarities between these entities. However, further studies are needed to account for variables such as the MRI device, the protocol used, patient age, and silicone implant age.
REFERENCIES