Breast Implants and the Reconstructed Breast

History in the United States

Silicone breast implants were introduced in 1964 by Cronin and Gerow ( ). 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 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, and there is no evidence of a relationship between silicone breast implants and breast cancer. At that 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 2007, a review article by McLaughlin et al. 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.” A subsequent study by showed no association with silicone breast implants and connective tissue disease. A separate meta-analysis of 17 studies representing 7 cohorts in 2015 showed no association between breast implants and risk of breast cancer ( ). There is, however, a rare but reported primary breast anaplastic large cell lymphoma (ALCL) seen in patients with implants. This rare lymphoma is a disease of the fibrous capsule surrounding the implant and not of the breast tissue around the implant.

The FDA reapproved and lifted the moratorium on silicone breast implants for both augmentation and reconstruction after extensive study and analysis in 2006. In a document issued by the FDA ( http://www.fda.gov/medicaldevices/deviceregulationandguidance/guidancedocuments/ucm071228.htm ), breast implant types, testing, and recommending the development of Core Study Clinical Data Groups to review patient cohorts of different breast implant types from manufacturers were described. The FDA recommended studying cohorts of patients separated into indications for primary augmentation, primary reconstruction, revision augmentation, and revision reconstruction at entry to review data of 10 years or more of prospective follow-up (this could include data with premarket and postmarket approval follow-up). On the FDA website (accessed February 2015), routine MRI evaluations in all patients at 1, 2, 4, 6, 8, and 10 years were recommended to monitor patients for silent rupture for the Core Studies for silicone breast implants. Many of the studies on breast implant complications and rupture now arise from FDA-recommended Core Study data.

Implant Types

There are several types of implants available in United States, in terms of material type, shape, surface texturing, and the number of chambers ( Table 9.1 ; Box 9.1 ). The most common breast implants are single-lumen silicone implants. Silicone implants are composed of a silicone elastomer shell filled with silicone made from a synthetic polymer of cross-linked chains of dimethyl siloxane, which makes the implant soft and movable. The inner silicone can be a gel, a liquid, or a solid form. The implant shape is either round or anatomic ( Fig. 9.1 ). The outer envelope can be textured (polyurethane coated) or smooth (uncoated; Fig. 9.2 ). Textured silicone implants are now comprised of first-generation through fifth-generation types ( Table 9.2 ). The newer generations of silicone implants are more stable and have had a very small rupture rate.

Saline implants are composed of an outer silicone shell and an inner envelope filled with saline. 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.

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 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, a by-product suspected to cause cancer in laboratory animals.

All implants are placed behind the breast tissue, and some implants are placed behind the pectoralis muscle ( Fig. 9.3 ).

Mammographic Limited-Compression Views and Implant-Displaced Views

An implant is not as compressible as breast tissue and can be ruptured if compressed too hard during either mammography (in breast imaging) or during closed capsulotomy (by the surgeon’s fingers). Because limited mammographic compression decreases visualization of cancers, the Mammography Quality Standards Act recommends two specific views of each implanted breast ( Box 9.2 ): one to look at the implant and one to look at the breast tissues for cancer. These two views include one limited-compression view that includes the implant and the tissue around it but does not use much compression (to not rupture the implant), and two implant-displaced views in which the technologist carefully strongly compresses only the breast tissue in front of the implant by carefully displacing the implant out of the field of view ( Figs. 9.4 and 9.5 ). The limited-compression mammogram in which the implant is surrounded by noncompressed breast tissue looks at both the breast tissue and the implant integrity. The second view, the strongly compressed tissue implant-displaced view, looks specifically at the breast tissue for cancer. However, even with the implant-displaced views, the radiologist sees only about 80% of the breast tissue because some breast tissue will always be hidden by the implant.

Normal Implants on Mammography

A normal silicone implant is quite dense and completely opaque and obscures and displaces much of the surrounding breast tissue. On mammography the silicone implant appears as a smooth, white oval opacity near the chest wall ( Fig. 9.4A ). Unlike opaque silicone implants, saline implants contain radiolucent saline surrounded by a dense silicone outer envelope ( Fig. 9.5A ). Wrinkles on saline implants are easily detected, unlike on opaque silicone implants, which are completely white ( Fig. 9.5A ). Wrinkles are normal findings that are accentuated by mammography because the implant envelope is easily folded when compressed ( Fig. 9.6 ). Another common type of implant is the saline outer, silicone inner double-lumen implant, which appears as an opaque opacity (inner silicone implant) surrounded by lucent opacity (outer saline lumen implant; Fig. 9.7 ).

Breast implants are always placed behind the breast tissue for augmentation. If the implant is behind the glandular tissue and on top of the pectoralis muscle, it is in the subglandular position. If the implant is behind the glandular tissue and behind the pectoralis muscle, it is in the subpectoral position (see Fig. 9.3 ). When an implant is in the subglandular position, the shadow of the pectoralis muscle is underneath the implant on the mediolateral oblique view ( Fig. 9.8A ). In contrast, the pectoralis muscle curves over the implant for implants placed in the subpectoral position ( Fig. 9.8B ).

The body generally forms a fibrous capsule around the implant, no matter what type of implant. The fibrous capsule is usually soft, nonpalpable, and undetectable to physical examination, but with time, the capsule may harden or calcify. On mammography, the fibrous capsule surrounding implants is not usually visible unless it calcifies. A calcified fibrous capsule contains dystrophic sheetlike calcifications and appears white, thin, and bumpy next to the implant on the nonimplant-displaced views ( Fig. 9.9 ). 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 they produce a typical fine mesh-like calcification ( Fig. 9.10 ). Implant-displaced views displace the capsular calcifications away from the implant. These views, with or without spot magnification, help analyze calcifications if the concern is that the calcifications are in the breast parenchyma rather than in the implant capsule.