The modified radical mastectomy (MRM), or traditional non-skin-sparing mastectomy (NSSM), most commonly performed today, was described by Madden in 1965. This procedure involves removal of all breast tissue, while preserving both pectoralis muscles, and it is commonly accompanied by dissection of level I and II axillary lymph nodes if indicated [3
]. A locoregional recurrence (LR) rate of roughly 10% at 5–8 years is deemed acceptable by many authors [4
], with most LR occurring within the first five postoperative years [5
The skin-sparing mastectomy (SSM) was first described in 1991 by Toth and Lappert [33
] as an effort to maximize skin preservation to improve cosmetic outcome and facilitate reconstruction. It typically entails removal of the entire breast and nipple-areola complex (NAC) while preserving the skin envelope and the natural inframammary fold [34
]. The dissection is carried out in the same plane as the NSSM and an effort to remove an equivalent amount of breast tissue as in NSSM should be made [35
]. The traditional SSM also involves excision of the skin overlying superficial tumors as well as previous biopsy entry sites to decrease chances of LR, however, this is not routinely performed by all surgeons [36
Naturally, leaving behind additional tissue is of concern when oncologic safety is imperative. The most common site for LR after conventional mastectomy is within the skin overlying the chest wall and LR often portends a poor prognosis [37
]. SSM is less ablative than NSSM, leaving behind superior and inferior skin flaps to preserve the natural skin envelope, however, the technique still requires the surgeon to remove as much breast tissue as possible, with dissection carried out above the superficial fascia, leaving behind only epidermis, dermis, and a small amount of subcutaneous fat. Diminished exposure and a larger area of increased residual skin make the procedure more technically demanding. Recent reports have characterized the histological characteristics of skin flap specimens. Identifying residual breast tissue or positive superficial margins carries with it concern for oncologic safety and equivalence at maintaining local control [40
Torresan et al. looked at the amount of residual breast tissue after SSM by histologically analyzing skin flap specimens, and they found 59.5% of specimens contained residual breast tissue, and 9.5% of skin flaps harbored residual disease [42
]. They also concluded that skin flaps >5
mm were associated with the presence of residual disease.
Ho et al. [44
] found 23% of analyzed skin flaps were involved with residual tumor, with the majority of involved skin flaps located directly over the tumor, and significantly associated with tumor size and the presence of skin tethering. Cao et al. histologically analyzed additional skin margins (ASM) taken at the time of SSM and found that 38% of 168 SSM's had a positive superficial specimen margin. A thicker ASM had residual breast tissue in 53% of cases, and it was an independent predictor of residual disease [45
It is imperative that the oncologic breast surgeon strives for clear margins, and yet few studies have reported on margin status after SSM and the literature is varied. Despite numerous studies previously mentioned, showing no statistical difference between NSSM and SSM in terms of LR, SSM has been shown to be an independent predictor of close or positive margins [42
]. Horiguchi et al. defined close margin as within 5
mm and did find margin status significant on multivariate analysis [47
]. Smaller specimen weight, smaller skin area, a lower skin/SSM surface ratio, an extensive insitu component, hormone receptor status, younger patient age, multiple ipsilateral tumors, palpable cancers, and tumor location (specifically the upper inner quadrant) have all been shown to be independent risk factors for positive margins in SSM (see ) [45
Local recurrence after skin-sparing mastectomy in stage IIB/III breast cancer.
Despite these findings showing relatively high rates of residual breast tissue with or without involved superficial margins, numerous studies over the past two decades have determined that SSM is an oncologically safe procedure with no significant difference in LR than NSSM [8
]. The LR after NSSM in tumors up to 4
cm was shown to be 10% after 20 years of followup [54
]. An extensive review of the literature has shown that SSM recurrence rates range from 0–7% [11
]. These studies include both prospective and retrospective design, and they are difficult to compare as they vary largely in patient sample size, stage of disease, tumor characteristics, adjuvant chemotherapy or radiation therapy, use and type of immediate or delayed reconstruction, and followup time. Several meta-analyses have concluded that SSM is an oncologically safe procedure, at least for early stage and small tumor size [35
Overall, as would be expected, LR after SSM is lower for smaller and low stage tumors with less invasive characteristics. LR after mastectomy for DCIS in most series is between 1–3% [56
]. Similarly, Slavin et al. [11
] had no recurrences over 45 months for 26 cases of SSM for DCIS. The series by Carlson [49
] included 175 cases of DCIS, and on subset analysis, after 65 months of followup, there was only one LR. These findings are supported by several other studies, summarized in .
Local recurrence after skin-sparing mastectomy in stage DCIS.
When T1 and T2 tumors were looked at specifically, Newman et al. [40
] reported a 6.2% recurrence after SSM and immediate reconstruction (IR) with a mean followup time of 26 months. This was in agreement with Kroll and Khoo [50
] who reported a 7% LR with SSM and IR, as compared to a 7.5% NSSM. The largest series by Carlson et al. mentioned previously involved 539 patients, with a mean followup of 65 months, and found that tumor size, nodal status, and LVI were all significant predictors of recurrence, with LR of 3, 10, and 11% for T1, T2, and T3 tumors, respectively [49
]. Medina Franco et al. [52
] also reported that tumor size, stage, lymph node involvement, and poor tumor differentiation were risk factors for LR, and they reported that after SSM, LR was 4.5% in 176 cancers with a median followup of 73 months. Spiegel and Butler [12
] followed patients for 9.8 years, and they reported an LR of 5.6% in 117 invasive cancers after SSM.
Studies of SSM in high-risk patients, particularly those with more advanced stage, have also been selectively performed, albeit in fairly small patient populations, however, have shown promising results, with recurrence rates between 2.6–4.6% [13
]. These results are summarized in .
Rate of NAC loss following NSM.
The majority of mastectomy patients do not require adjuvant radiotherapy, however, those with more than three positive regional nodes or larger tumors are often offered radiotherapy in addition to mastectomy [60
]. SSM is most often studied as an alternative to NSSM, however, with preservation of the skin envelope, unlike NSSM, SSM mandates a reconstructive procedure. Previously, SSM had been avoided in situations that require adjuvant radiotherapy because of the risk of complications associated with radiotherapy and immediate reconstruction (IR), with rates that vary from 5–16% [61
]. While the different types of reconstructive procedures performed with SSM are beyond the scope of this review, complications have been diminished by use of a temporary tissue expander placed underneath the pectoralis major at the time of IR. At a second operation, the expander is replaced with a permanent implant or delayed reconstruction using a myocutaneous flap is performed after the area has been irradiated, protecting the flap from damage [61
]. While capsular contraction has been reported as a common response to adjuvant radiation after implant or expander placement [62
], Hughes et al. found that skin-sparing mastectomy followed by irradiation did increase the rate of reoperation and did not lead to significant increase in complications or capsular contracture rates [62
]. Furthermore, despite having adjuvant radiotherapy, patient satisfaction scores regarding aesthetic outcome remain high. [63
SSM is an oncologically safe procedure with LR rates comparable to NSSM for small and low-grade tumors, and the literature suggests this may also be true for tumors of higher grade and stage. Margins after SSM are as important, if not more important than after NSSM because of the decreased operative exposure and the technique to make adequately thin skin flaps make obtaining clear margins more difficult. The surgeon should be aware of risk factors for positive margins after SSM in order to be vigilant about an adequate cancer extirpation. Because of the preservation of the skin envelope, SSM does require reconstruction be performed at the time of the mastectomy. While adjuvant radiotherapy in the setting of IR after SSM is not preferred given higher rates of complications such as fat necrosis or capsular contracture, techniques such as IR with tissue expander placement can diminish complication rates and maintain the improved aesthetic outcomes that SSM can offer over NSSM.