Histological comparison between irradiated and non-irradiated breasts in breast reconstruction
Comparação histológica entre mamas irradiadas e não irradiadas em reconstrução mamária

INTRODUCTION

Since the 1990s, the treatment of breast cancer has included not only curative therapies but also breast reconstruction, which has increased patients’ interest in getting protected from cancer and obtaining better aesthetic results. Many studies have reported that breast reconstruction has no negative impact on cancer safety, reassuring patients and motivating them to perform the procedure^1,2.

Studies show that radiotherapy, an adjuvant strategy, provides favorable outcomes by reducing the rate of recurrence of the disease, thus increasing the number of indications. The guidelines for radiotherapy began to include more diverse indication criteria, further expanding the use of this therapeutic modality^3,4.

Immediate reconstruction is indicated because it can significantly improve the quality of life of a woman, helping in her body image satisfaction and psychosocial well-being, compared to delayed reconstruction⁵.

Breast reconstruction using implants is a relatively simple procedure, with short surgical time and rapid postoperative recovery. It also provides excellent aesthetic results. Its advantages compared to autologous flap reconstruction include smaller procedures with good results, without the need to transpose skin islands from other regions of the body to the breast^6,7. Given these facts, it is currently one of the most popular surgical methods. The increasing indication of breast reconstruction with implants, combined with the full application of radiotherapy, have made it more difficult to understand and avoid potential complications associated with the interaction between radiation and implant. Capsular contracture, infection, and poor positioning of the breast implant were indicated as the main complications. Although capsular contracture is the most important complication, being the most common cause of reoperation,^3,8,9 its pathogenesis induced by radiation is still unknown¹⁰.

Some of the skin changes after irradiation have been investigated, and early effects (up to 90 days after the onset of radiation) include dehydration, pigmentation changes, loss of skin appendages, erythema, and desquamation. Delayed histological changes (after 90 days) include atrophy or hyperplasia of the epidermis, hypocellular fibrosis of the dermis, sclerotic vascular changes, and absence of pilosebaceous units (appendages). However, it is still unclear whether these changes are associated with the difficulties and complications of breast reconstruction with expander/implant^11,12. The susceptibility of the skin to changes after irradiation can be determined genetically. This concept is reinforced by individual differences in changes caused by radiation and developed complications^13,14,15.

This study aimed to describe and compare histological differences between skin, subcutaneous cell tissue, pectoralis major muscle, and capsule of irradiated and non-irradiated breast implant in the same patient and to guide further studies to analyze possible methods of prophylaxis and treatment of complications. Currently, there are no studies that address such comparisons on all tissue layers.

METHODS

RESULTS

The data from 7 patients, all female, with a mean age of 52.15 years (ranging from 34 to 68 years) were analyzed. They received 25 sessions of conventional radiotherapy in one breast, with a total dose of 50 Gy. The mean time between the last radiotherapy session and breast reconstruction was 54.14 months (ranging from 7 to 204 months). One of the postoperative complications of the first surgery was capsular contracture, which affected all patients and led to the second surgical period. One patient had suture dehiscence on both breasts, which was resolved with local bandages. None of them had infections.

While skin and subcutaneous cell tissue biopsies were collected in all patients, capsule and pectoralis major muscle biopsies were also collected, since the breast contralateral to radiotherapy did not receive the implant. The main clinical and macroscopic changes during the surgical procedure were as follows: dry skin (100%), loss of skin elasticity (85.71%), hypovascularized fat (100%), capsular contracture (100%), capsular thickening (85.71%), muscle hypotrophy (100%), hypovascularized muscle (85.71%), and skin dyschromia (42.85%), as shown in Table 1.

Table 1 - Macroscopic clinical and intraoperative changes of the irradiated breast.

The main histological findings in the skin and subcutaneous cellular tissue in the irradiated breast were as follows: epidermal hyperplasia (71.42%), flattening of the papillary layer (85.71%), atrophy of the skin appendages (100%), vascular congestion in fatty tissue (71.42%), high density of skin collagen fibers (100%), hyalinization of vascular walls (85.71%), reduction of elastic fibers in the deep dermis (85.71%), and unidirectional alignment of collagen fibers (100%), as shown in Table 2. These findings were observed in the samples of irradiated skin with considerable differences.

Table 2 - Anatomopathological findings of skin and subcutaneous cellular tissue.

The main histological findings of capsule and pectoralis major muscle in the irradiated breast were as follows: lower density of elastic fibers (80%), perivascular fibrosis (100%), synovial metaplasia (100%), skeletal muscle sequestration at the interface with the capsule (80%), capsular hyalinization (80%), and capsular fibrosclerosis (100%), as shown in Table 3.

Table 3 - Anatomopathological findings of implant capsule and pectoralis major muscle.

All patients had similar anatomical findings, which were consistent with clinical findings. It should be mentioned that cases 5 and 7 had more discreet anatomopathological findings, occasionally having a mixed pattern of presentation with areas containing normal tissue in the irradiated breast. Figures 1, 2, 3, and 4 show the main histological differences between irradiated and non-irradiated breasts.

Figure 1 - Histological comparison of the skin of non-irradiated. A: and irradiated. B: Breasts. Emphasis for the greater density of elastic fibers in normal skin (green arrow), for the unidirectional arrangement of elastic fibers in irradiated skin (black arrows), and for the presence of skin attachments in normal skin (blue arrow).

Figure 1 - Histological comparison of the skin of non-irradiated. A: and irradiated. B: Breasts. Emphasis for the greater density of elastic fibers in normal skin (green arrow), for the unidirectional arrangement of elastic fibers in irradiated skin (black arrows), and for the presence of skin attachments in normal skin (blue arrow).

Figure 2 - Histological comparison of subcutaneous cell tissue of non-irradiated. A: Irradiated. B: Breasts. Emphasis for the hyalinization of vascular wall in the irradiated breast and the preservation of fine and delicate walls in the capillaries of the non-irradiated breast (black arrows) and the vascular congestion observed in the irradiated breast (blue arrow).

Figure 2 - Histological comparison of subcutaneous cell tissue of non-irradiated. A: Irradiated. B: Breasts. Emphasis for the hyalinization of vascular wall in the irradiated breast and the preservation of fine and delicate walls in the capillaries of the non-irradiated breast (black arrows) and the vascular congestion observed in the irradiated breast (blue arrow).

Figure 3 - Histological comparison of the capsules of non-irradiated. A: Irradiated. B: Breasts. Emphasis for the greater thickness of the capsule in the irradiated breast (black arrow) and for fibrosclerosis and subcapsular hyalinization in the irradiated breast (blue arrow).

Figure 3 - Histological comparison of the capsules of non-irradiated. A: Irradiated. B: Breasts. Emphasis for the greater thickness of the capsule in the irradiated breast (black arrow) and for fibrosclerosis and subcapsular hyalinization in the irradiated breast (blue arrow).

Figure 4 - Histological comparison of muscle tissue and its neurovascular plexus in non-radiated. A: Irradiated. B: Breasts. Emphasis for the more organized and circular aspect of the arterioles in the irradiated breast, as well as perivascular fibrosis (black arrows).

Figure 4 - Histological comparison of muscle tissue and its neurovascular plexus in non-radiated. A: Irradiated. B: Breasts. Emphasis for the more organized and circular aspect of the arterioles in the irradiated breast, as well as perivascular fibrosis (black arrows).

Clinical cases

Case 1

A 36-year-old patient, without comorbidities, diagnosed with invasive ductal carcinoma in the right breast, undergoing neoadjuvant chemotherapy + bilateral mastectomy without preservation of nipple-areola-complex, with right axillary dissection + immediate reconstruction with retromuscular remote valve expanders, in February 2016, without complications. Expansion was performed with physiological solution until March 2016 and adjuvant radiotherapy was performed in the right breast (last session in June 2016). Submitted to second surgical period in February 2017 for replacement of expander by silicone implants + bilateral reconstruction of nipple-areola-complex + liposuction of axillary extensions without complications. Due to the development of intense radiodermatitis not responsive to clinical treatments, she underwent microsurgical reconstruction of the right breast with transverse flap of the rectus abdominis muscle in June 2019, as shown in Figure 5.

Figure 5 - JSFB, 37th month postoperatively. Bilateral mastectomy without preservation of nipple-areola complex, with right axillary dissection + immediate reconstruction with retromuscular remote valve expanders and 25th month postoperatively expander replacement by silicone implants + bilateral reconstruction of nipple-areola complex + liposuction of axillary extensions.

Figure 5 - JSFB, 37th month postoperatively. Bilateral mastectomy without preservation of nipple-areola complex, with right axillary dissection + immediate reconstruction with retromuscular remote valve expanders and 25th month postoperatively expander replacement by silicone implants + bilateral reconstruction of nipple-areola complex + liposuction of axillary extensions.

Case 2

A 41-year-old patient with no comorbidities, diagnosed with invasive carcinoma in the left breast, undergoing left mastectomy with sentinel lymph node biopsy (negative) and contralateral prophylactic mastectomy + immediate reconstruction with retromuscular silicone implants with lower pole amputation (Torek) in December 2017, without complications. She underwent adjuvant radiotherapy in the left breast (last session in August 2018), and the second surgical period in June 2019 for left capsulotomy + implant repositioning, fat grafting for symmetrization and correction of scars in axillary extensions (reconstruction of nipple-areola complex programmed in the third period) without complications as shown in Figure 6.

Figure 6 - QNPO, 9th month postoperatively. Left mastectomy with sentinel lymph node biopsy (negative) and contralateral prophylactic mastectomy + immediate reconstruction with retromuscular silicone implants with lower pole amputation (Torek).

Figure 6 - QNPO, 9th month postoperatively. Left mastectomy with sentinel lymph node biopsy (negative) and contralateral prophylactic mastectomy + immediate reconstruction with retromuscular silicone implants with lower pole amputation (Torek).

DISCUSSION

As a result of early detection and improvement in treatments such as surgery, hormonal therapies, chemotherapy, and radiotherapy, the mortality rate for breast cancer has been decreasing since the 1950s. Therefore, more patients with breast cancer are surviving and remaining with sequelae that must be treated. In this study, we sought to describe the histological differences of skin, subcutaneous cell tissue, implant capsule and pectoralis major muscle between irradiated and non-irradiated breasts of the same patient. Previous studies have addressed only the skin and subcutaneous region.

The findings of epidermis hyperplasia, flattening of the papillary layer, atrophy of the skin appendages, high density of the skin collagen fibers, and presence of unidirectional collagen fibers had already been reported^11,12. Atrophy of skin appendages is of particular clinical importance, as loss of sebaceous tissue and sweat glands lead to dehydrated skin, resulting in the need for long-term skincare using moisturizers. Chronic radiation dermatitis is reported to be associated with fibroblast atypia, which is not seen in other types of fibrosis, such as third-degree burn scars^12.13. The present study corroborates these findings. Other findings included the following: reduction of elastic fibers in the deep dermis, vascular congestion in fatty tissue, and hyalinization of vascular walls. Although histological changes in dermatitis due to radiation have already been described^12,13, these have been considered to be less important clinically with acceptable side effects. However, this does not apply when planning breast reconstruction with silicone expander/implant.

Archambeau et al., in 1995¹¹, found skin changes due to irradiation progressing for up to 10 years. Given this fact, the delay in indicating reconstruction after radiotherapy does not increase safety. This finding could explain the mild findings found in cases 5 and 7, in which the last radiotherapy session was more recent (10 and 8 months, respectively).

One of the main complications of radiotherapy is fibroproliferation of the capsular tissue around the implant with a resulting capsular contracture. This leads to an inadequate expansion with distortion and undesirable aesthetic results, sometimes causing additional surgery. Currently, the pathogenetic mechanism of fibroproliferation and capsular contracture induced by radiation is unknown. The correct anatomical description of the observed changes can help in the development of new studies, unraveling the biochemical mechanisms involved in this pathogenesis.

Understanding the pathogenesis of the fibroproliferative process, which starts with the expansion of the tissue previously subjected to radiotherapy, may probably lead to the discovery of prevention strategies or clinical treatment. For example, COX-2 selective inhibitors are commercially available and were effective in partially decreasing cell proliferation in fibrosis models mediated by increased catenin levels¹⁷. There is great potential to explore treatment protocols in an animal model and eventually in clinical trials.

Encapsulation occurs as a result of an inflammatory response to the presence of the foreign body, and fibrosis progresses to nearby tissues. When fibrosis progresses excessively, due to the persistence of the inflammatory response and exposure to external risk factors, contracture occurs around the thickened capsule¹⁸.

Therefore, breast reconstruction with implants is performed under the assumption that if radiotherapy is administered, capsular contracture will be recognized as a fundamental limitation, and many studies will be conducted to find solutions to this question.

Kim et al., in 2018¹⁹, confirmed that the infiltration of myofibroblasts was promoted in irradiated mice, suggesting that this phenomenon acts as a catalyst to accelerate the progression of contracture. We did not find this type of cellular infiltration in any of the samples of irradiated breast.

Some studies reported using coverage with acellular skin matrix and some medications such as montelukast, antileukotrienes, and steroids to reduce the occurrence of capsular contracture around textured implants^20,5. Although it is consensus that radiation can induce fibroproliferation in skin and subcutaneous tissues^11,13, the relative occurrences of specific molecular mechanisms are still unclear.

We believe that dry skin may be related to atrophy of the skin appendages. The loss of skin elasticity was related to the reduction of elastic fibers in the deep dermis, epidermal hyperplasia, flattening of the papillary layer, high density of skin collagen fibers, and unidirectional alignment of collagen fibers. Hypovascularized fat was related to subcutaneous vascular congestion and hyalinization of vascular wall. The thickened and contracted capsule was related to lower density of elastic fibers, capsular hyalinization, capsular fibrosclerosis, and synovial metaplasia. Hypotrophic and hypovascularized muscle was related to perivascular fibrosis and skeletal muscle sequestration by capsule.

With the data obtained so far, it is not possible to establish a cause and effect relationship, but we will continue to include new patients into the study and try to optimize the quantitative analysis of the information to get to this point. Since each histological evaluation was performed between the breasts of the same patient and not between two different groups, even a small number of patients provided significant results.

CONCLUSION

We found common histological changes in irradiated breasts in most patients. These findings are compatible with the clinical and macroscopic changes observed. This is a descriptive study that presents itself as a pilot for the development of new studies investigating the physiopathological mechanisms related to the described histological changes, thus proposing methods of prophylaxis and treatment for the complications of radiotherapy.