Chapter 9 Breast Implants and the Reconstructed Breast

Silicone breast implants were introduced in 1962. An estimated 2 million women in the United States have silicone breast implants, with approximately 80% placed for breast augmentation and the remainder for breast reconstruction after mastectomy. On April 16, 1992, the U.S. Food and Drug Administration (FDA) restricted the use of silicone implants to women undergoing breast reconstruction for mastectomy because of concern about implant rupture and a possible association with connective tissue disease.

Addressing these concerns, an article by Tugewell and colleagues in 2001 reported a U.S. District Court order establishing a national science panel to assess whether existing scientific studies showed an association between silicone breast implants and connective tissue disease. They concluded that no scientific evidence of such a relationship exists, nor is there evidence of a relationship between silicone breast implants and breast cancer. At this time, silicone gel breast implants were used for breast reconstruction after mastectomy in the United States. Saline-filled implants were used for cosmetic breast augmentation.

In 2006, a review article by McLaughlin and colleagues restated that there was no “causal association between breast implants and breast or any other type of cancer, definite or atypical connective tissue disease, adverse offspring effects, or neurologic disease.” The FDA re-approved silicone breast implants for both augmentation and reconstruction after extensive study and analysis, but still requires careful patient tracking. This chapter reviews breast implants, implant rupture, and the reconstructed breast.

Implant Types

The most common breast implants are single-lumen and filled with either silicone or saline. Silicone implants are composed of a silicone elastomer shell filled with silicone made from a synthetic polymer of cross-linked chains of dimethylsiloxane that makes the implant soft and movable (Box 9-1 and Fig. 9-1). The outer envelope can be textured or smooth, polyurethane-coated or uncoated. The inner silicone can be a gel, a liquid, or a solid form. Saline implants are composed of an outer silicone shell and an inner envelope filled with saline (Fig. 9-2A to D). Of note, newer generation silicone implants have had a very small rupture rate in augmentation patients. Double- or triple-lumen implants have two or more envelopes inside one another, and each can contain saline or silicone gel. A common double-lumen implant is the saline outer, silicone inner implant. More recent common double-lumen implants have silicone outer and saline inner components. All implants are placed behind the breast tissue, and some implants are placed behind the pectoralis muscle.

Box 9-1 Implant Types

Single-lumen silicone

Single-lumen saline

Double-lumen: saline outer, silicone inner

Single-lumen silicone, outer polyurethane mesh coating

Single-lumen, lipid-filled

Complex or custom implants

Stacked implants

Direct silicone or paraffin injections

Figure 9-1 Normal silicone implant. A, A silicone gel implant photographed from the side. The implant will be placed underneath the breast tissue and either on top of or underneath the pectoralis muscle at surgery. B, Mammogram shows a dense structure near the chest wall and a little breast tissue around it. C, Ultrasound of a typical intact silicone implant shows the breast tissue in the near-field and the oval hypoechoic implant near the chest wall. Note that the appearance of a normal silicone implant is almost anechoic and simulates a very, very large cyst. D, Ultrasound of an intact silicone implant shows a typical normal edge artifact causing shadowing where the edge of the implant meets breast tissue. Typical normal reverberation artifact is seen in the near-field of the implant, similar to artifacts seen in a normal urinary bladder.

Figure 9-2 A to D, Normal saline implant: standard and implant-displaced mammograms. Mediolateral oblique (MLO) (A) and craniocaudal (CC) (B) mammograms with a saline implant show the implant behind the pectoralis muscle. The silicone envelope surrounds the lucent saline filling, so that the wrinkles within its envelope and the ringlike injection port are visible. In contrast, a silicone implant is completely white. MLO (C) and CC (D) implant-displaced mammograms show well-compressed breast tissue anterior to the implant. The technologist obtains the implant-displaced view by pinching the breast tissue in front of the implant, compressing the breast tissue for optimal visualization without rupturing the implant. E, Schematic of implant placement: subglandular implant placement (left) and subpectoral implant placement (right). F, Schematic of implant complications. On the left, a fibrous capsule forms around an intact implant. In the middle, the implant shell may rupture, but the silicone is contained in the fibrous capsule—called intracapsular rupture. On the right, the implant capsule and the fibrous capsule are ruptured, with silicone outside the fibrous capsule—called extracapsular rupture.

Less common implants include those filled with a polyvinyl alcohol sponge or a lipid substance (Trilucent implant), the latter of which may show a serous/lipid level on magnetic resonance imaging (MRI) if ruptured. “Stacked” implants are two single-lumen implants placed one on top of the other in the breast for aesthetic purposes. An implant type that is no longer used was covered with a finely textured meshlike surface over the outer envelope that was composed of a polyurethane-coated material to prevent fibrous capsular formation. This implant was banned because of the release of 2,4-toluenediamine (TDA), a byproduct suspected to cause cancer in laboratory animals.

Mammography of Normal Implants

Surgeons place silicone gel-filled implants behind the breast tissue on the chest wall in the subglandular or subpectoral position (see Fig. 9-2E and F). In either case, the body generally forms a fibrous capsule around the implant. The fibrous capsule is usually soft, nonpalpable, and undetectable to physical examination, but with time, the capsule hardens or calcifies in some individuals. If a silicone implant ruptures, this fibrous capsule holds the silicone within as long as it, too, does not rupture.

A normal silicone implant is quite dense and completely opaque, and obscures and displaces much of the surrounding breast tissue. On mammography the implant appears as a smooth white oval opacity near the chest wall (Fig. 9-3). The pectoralis muscle curves over the implant in subpectoral implants and lies underneath the implant in subglandular implants. A silicone gel-filled implant is not as compressible as breast tissue and can be ruptured if compressed too hard during mammography or closed capsulotomy. Because limited compression decreases visualization of the surrounding breast tissue for breast cancer screening, the Mammography Quality Standards Act (MQSA) recommends four views of each implanted breast. Two views are implant-displaced views, in which the technologist pinches the breast tissue in front of the implant to compress it, and two views include the implant but do not use much compression (Box 9-2). Breast tissue is evaluated on the implant-displaced views; implant integrity is evaluated on limited-compression mammograms in which the implant is surrounded by noncompressed breast tissue. Even with the implant-displaced views, the radiologist sees only about 80% of the breast tissue because it is hidden by the implant.

Figure 9-3 Normal silicone implant: standard and implant-displaced mammograms. Mediolateral oblique (MLO) (A) and craniocaudal (CC) (B) mammograms with subglandular silicone implants show the implant as a white structure near the chest wall and the relatively uncompressed breast tissue anterior to it. The technologist uses very little compression on these images to avoid rupturing the implant, but it is hard to find breast cancer in uncompressed breast tissue. Implant-displaced MLO (C) and CC (D) mammograms show well-compressed breast tissue anterior to the implant. Note that the breast tissue is spread apart on the implant-displaced views, making it easier to find early cancer. However, even with the best implant-displaced views, the radiologist can see at most only 80% of the breast tissue because the implant obscures the rest.

Box 9-2 Mammography of Implants

Four views of each breast:

CC and ML or MLO with the implant

CC and ML or MLO implant-displaced views

Magnification, spot, and other fine-detail views can be performed in the implanted breast

5% of screenings show asymptomatic rupture

CC, craniocaudal; ML, mediolateral; MLO, mediolateral oblique.

The implant-displaced technique does not completely resolve the problem of imaging small breast cancers, but it does optimize the amount of breast tissue displayed on the mammogram. Both physical examination and breast ultrasound as an adjunct to mammography are helpful in evaluating mammographically detected breast masses or palpable findings because mammography is limited with implants in place. Ultrasound can be especially helpful in determining whether a true mass exists, because ultrasound can evaluate the entire breadth of the breast tissue down to the implant. Ultrasound also distinguishes breast masses from the snowstorm appearance of silicone granulomas caused by ruptured implants (Fig. 9-4).

Figure 9-4 Mammogram with standard and implant-displaced views, with cancer present. A, Notice that the dense silicone implant near the chest wall obscures most of the breast tissue in this patient with a palpable mass at the 12-o’clock position of the right breast. B, Even when the implant is displaced, not all the breast tissue can be seen. C, At the 12-o’clock position of the right breast, ultrasound shows a suspicious irregular mass containing calcification on the fibrous capsule of the implant, not seen on the mammogram because it was pushed away from the field of view on the compressed images. Biopsy revealed invasive ductal cancer.

Unlike opaque silicone implants, saline implants contain radiolucent saline surrounded by a dense silicone outer envelope, in which small wrinkles may be seen. When a saline implant ruptures, the saline diffuses into the breast tissue and the envelope shrinks back against the chest wall (Fig. 9-5). In contradistinction, when a silicone implant ruptures, most of the silicone may be contained by the fibrous capsule and the implant retains much of its shape and volume. Saline outer, silicone inner double-lumen implants have an outer envelope containing saline surrounding a dense inner silicone implant filling.

Figure 9-5 Ruptured saline implant. Mediolateral oblique (MLO) (A) and craniocaudal (CC) (B) mammogram with a saline implant in place shows the saline implant near the chest wall and a typical ringlike portion of the implant (arrow). A year later, the patient thought her breast suddenly got smaller after a car accident. MLO (C) and CC (D) mammograms show that the saline implant ruptured. Note the collapsed saline envelope at the chest wall (arrow).

The fibrous capsule surrounding implants of any type is not usually visible unless it calcifies. A calcified fibrous capsule contains dystrophic sheetlike calcifications and appears bumpy on the nondisplaced-implant views (Fig. 9-6A). Implant-displaced views displace the capsular calcifications away from the implant for analysis if one is concerned that the calcifications are in breast parenchyma rather than in the implant capsule. Spot magnification mammograms also help the radiologist analyze intraparenchymal calcifications and distinguish them from capsular calcifications.

Figure 9-6 Calcifications near implants. A, Mediolateral oblique (MLO) mammogram shows two “stacked” implants in close proximity to each other with dense calcifications in the fibrous capsule that make the implant surface look bumpy. B, In another patient, capsular calcifications in a line mimic ductal carcinoma in situ. Biopsy showed dystrophic calcifications in the retained fibrous capsule after the implant was removed. C, An implant-displaced MLO mammogram shows a subpectoral saline implant in another patient and a calcified fibrous capsule from a previously removed subglandular polyurethane-covered implant. Notice the dystrophic sheetlike calcifications around the previous implant cavity. D, Tiny meshlike microcalcifications were seen near the dystrophic implant capsule and were removed by preoperative needle localization, as seen on specimen radiography; these microcalcifications represented the calcifying mesh of the outer polyurethane coating.

If an implant ruptures, the surgeon removes the ruptured implant but does not always remove the fibrous capsule. If the fibrous capsule has calcified, the mammogram shows dystrophic calcifications in a sheetlike curvilinear pattern because they reside in the retained fibrous capsule. These calcifications can be hard to distinguish from cancer and can prompt biopsy (see Fig. 9-6B). Another specific type of capsular calcification that can be mistaken for cancer and will sometimes prompt biopsy is from calcifying polyurethane-covered implants. These implants are covered with a spongelike material, and when they calcify produce a typical fine meshlike calcification that can mimic ductal carcinoma in situ (see Fig. 9-6C and D).

When evaluating breast tissue for cancer in women with implants, it is important to inspect both the implant-displaced views and the breast tissue adjacent to the implant on the nonimplant-displaced views. The standard views may display a mass near the implant or the fibrous capsule not evident on implant-displaced views. Masses on the fibrous capsule can be pushed away from the field of view with the implant-displaced views (Fig. 9-7). However, for masses or suspicious calcifications, spot compression or other fine-detail views can be used in women with implants, just as with any other woman. Needle localization, ultrasound-guided core biopsy, and stereotactic core biopsy all can be performed in women with implants as well. The radiologist just has to obtain informed consent from the woman, including implant rupture as a possible complication for percutaneous biopsies.

Figure 9-7 Craniocaudal (CC) (A) and mediolateral oblique (MLO) (B) mammograms; a dense mass is seen near the implant in the upper portion of the right breast on the MLO view only. The mass is obscured by the implant on the CC view. C and D, Photographically magnified views of the upper portion of the right breast taken in 1999 (C) and 2002 (D) show that the mass is new and developing in a previous biopsy site; the mass was not seen on implant-displaced views because it was pushed away with the implant, thus showing the importance of analyzing mammograms that include the implant as well as the implant-displaced view. Transverse (E) and longitudinal (F) ultrasound images show a spiculated mass immediately on top of the implant. G, Core biopsy under ultrasound guidance revealed invasive ductal cancer.

Implant Complications and Rupture

Untoward complications associated with silicone gel-filled breast implants include contracture of the fibrous capsule, calcification of the fibrous capsule, hematoma, infection, implant rupture, and the controversial silicone gel “bleed,” in which silicone gel leaks outside the implant through an intact envelope (Box 9-3). Capsular contracture is the most common complication, with a reported incidence of more than 70% in some older series and only about a 20% incidence in more recent series.

Box 9-3 Untoward Effects of Breast Implants

Rupture

Contraction of the fibrous capsule

Hematoma

Infection

Silicone gel “bleed”

Calcification of the fibrous capsule

Implants can undergo capsular contraction, becoming hard and resistant, leading to a round, hard appearance and feel. The Baker classification of capsular formation on implants describes increasing levels of capsular contracture (Table 9-1). The incidence of capsular contracture may be diminished by the use of textured submuscular implants, although the use of such implants remains controversial. Open surgical capsulotomy, in which the hardened implant capsule is removed, was used to solve the problem of capsular contracture. Alternatively, surgeons would squeeze the implant to break the hardened fibrous capsule to allow the implant to become soft and pliable again, called closed capsulotomy. Unfortunately, closed capsulotomy could result in implant rupture.

Table 9-1 Baker Classification

Different types of fillers for implants were examined in trials, resulting in varying rates of fibrous capsule contracture. Munker and colleagues reported on Trilucent implants in 27 patients who elected to exchange their implants for a fourth-generation cohesive silicone implant. Of these 27 patients, 14 had a change in the volume of their implants but not all were aware of the change, and capsular contracture was not present (Baker grade II) (see Table 9-1); 55% of the implants had thickening or color changes caused by peroxidation of the triglyceride contents, and the implant capsule was adherent to breast tissues—in particular, the pectoralis muscle, which led to prolonged operative times. Rizkalla and colleagues reported similar results, with a reoperation rate of 20% (10/50) and an implant deflation rate of 10% (5/50). The Medical Devices Agency in the United Kingdom (which merged with the Medicines Control Agency in April 2003 to form the Medicines and Healthcare Products Regulatory Agency) withdrew the Trilucent implant from the market in March 1999, with a subsequent recommendation in June 2000 that the implants be removed from patients. A new type of alloplastic material for implants that contains carboxymethylcellulose, called Hydrogel, was introduced into the European market. Of 12 patients with 20 implants placed between 1996 and 1997, as reported by Cicchetti and colleagues, none showed immediate complications and had Baker grade I or II capsular contracture at 3.5 years of follow-up.

Implant Rupture

Reports attribute implant failure to a subpectoral location and implant age, especially implants manufactured in the late 1970s and early 1980s (i.e., second-generation implants). Closed capsulotomy, or manual breaking of the fibrous capsule, is also associated with implant rupture.

Implant integrity is classified as intact, intact with gel bleed, intracapsular rupture, or extracapsular rupture (Table 9-2). Extracapsular rupture is defined as implant rupture with silicone gel extruded outside a broken fibrous capsule. Intracapsular rupture is defined as implant rupture with silicone gel still contained within an intact fibrous capsule. Gel bleed is defined as silicone gel leakage through an intact implant envelope, although the existence of gel bleed versus small, undetected ruptures remains controversial.

Table 9-2 Implant Rupture Types

Rupture Types	Silicone Location	Envelope Status
Intracapsular rupture	Fibrous capsule contains silicone gel	Envelope ruptured
Extracapsular rupture	Silicone gel outside fibrous capsule	Envelope ruptured
Gel bleed (controversial)	Silicone outside envelope	Envelope intact

A clinical diagnosis of implant rupture is often difficult to make. Feng and Amini report significant risk factors for implant rupture as an older implant ages: retroglandular location, capsular contracture, local symptoms, implant type (double-lumen and polyurethane-covered implants rupture less frequently than smooth gel implants), and manufacturer. The clinical history, signs, and symptoms are frequently nonspecific. In one series of 19 symptomatic patients with ruptured implants, women complained of palpable axillary, breast, or chest wall masses; pain; or changes in the size, shape, or texture of the breast. In one surgical series, 3 of the 32 patients reviewed were asymptomatic. Because physical examination misses approximately 50% of ruptures, clinicians have turned to imaging to help diagnose ruptured implants when the clinical findings are questionable.

Implant Imaging

Mammography

A retrospective review of screening mammograms in 350 asymptomatic women with breast implants showed an incidence of asymptomatic implant rupture of 5%. Mammography shows extracapsular rupture as silicone extravasation outside the implant envelope with blobs of silicone in the breast tissue (Fig. 9-8A and B), within implant ducts, or as a contour abnormality caused by extruded silicone in contiguity with the implant (Table 9-3). After extracapsular rupture, the surgeon removes the implant. Removal of all extravasated silicone is often impossible without removing much of the breast tissue, so the surgeon may leave some extravasated silicone in the breast. Later, when a new silicone implant is placed, residual silicone from the old ruptured implant makes it impossible to tell on mammography if the new implant has ruptured (see Fig. 9-8C). Silicone within axillary lymph nodes implies extravasation of silicone outside the fibrous capsule, because the silicone has traveled to the lymph nodes. This means that there must be an extracapsular rupture as well (see Fig. 9-8D).

Figure 9-8 Implant rupture. A, Mediolateral oblique (MLO) mammogram shows blobs of silicone extruded into tissue inferior to the implant on an analog mammogram. B, This patient felt a mass in her upper right breast, marked by a BB and showing extruded silicone above the implant on a digital mammogram. C, In another patient, digital MLO mammograms show retained silicone in the upper breasts after removal of ruptured bilateral silicone implants. If the patient replaces the silicone implants, new ruptures would be impossible to diagnose. D, After rupture and removal of silicone implants and replacement with saline implants, this patient has retained silicone in her lymph nodes bilaterally. E, A craniocaudal mammogram shows an unusual bulge of the implant’s outer contour that represents either rupture or a herniation of the implant through a tear in the fibrous capsule; surgery showed rupture. F, Ultrasound shows echodense noise or snowstorm sign over the bulge in part E, confirming a rupture.

Table 9-3 Imaging Findings with Rupture

Silicone implant contour lobulation indicates either capsular contracture, herniation of an intact implant envelope through a break in the surrounding fibrous capsule, or a contained implant leak (Table 9-4). Because intracapsular rupture is defined as implant rupture with silicone gel still contained within an intact fibrous capsule, mammography may show an intracapsular rupture as a normal-looking or bulging implant, depending on the shape of the fibrous capsule. Because both implant lobulation and a contained leak have the same mammographic appearance, radiologists use ultrasound and MRI to make the diagnosis of a rupture (see Fig. 9-8E and F). Mammography cannot identify intracapsular ruptures when the implant contour is normal, nor can it show posterior implant ruptures on the chest wall.

Table 9-4 False-Positive Imaging Findings for Rupture

Imaging Modality	Sign	Differential Diagnosis
Mammography	Implant contour deformity	Contained rupture Capsular contracture Herniation through a capsule tear
Mammography	Intraparenchymal silicone	Previous leak with the ruptured implant removed
Ultrasound	Stepladder sign	Intracapsular rupture Intact multilumen implant
MRI	Linguine sign Water droplets (occasionally seen)	Intracapsular rupture Intact multilumen implant