Nipple-sparing mastectomy (NSM) has now entered the mainstream for both the treatment and prevention of breast cancer. It is not however, the standard of care for either. NSM in the past was known as subcutaneous mastectomy. In the 1970's, subcutaneous mastectomy was occasionally performed for fibrocystic disease, breast cancer prevention and less frequently for cancer. By the 1980's, reports of cancer occurring in the residual breast tissue led the procedure into disfavor. It was not until the last several years that this procedure was essentially reborn as nipple-sparing mastectomy.
In examining the studies of subcutaneous mastectomy done in prior decades it was apparent that there were several problems that led to relatively poor results. Most importantly, most subcutaneous mastectomies of the 1970's were performed with a focus on cosmetics and less concern about removing a maximum amount of breast tissue. In many instances breast tissue was left behind intentionally to improve cosmetic results and to prevent necrosis (death) of the nipple.
NSM is now usually performed by a surgical oncologist, breast surgeon or general surgeon with a focus on maximizing breast tissue removal, while still attempting to maximize the cosmetic outcome. The term "nipple-sparing mastectomy" now refers to a more radical removal of breast tissue than was carried out during the subcutaneous mastectomy era. There has never been a comparative study that compares nipple-sparing mastectomy with standard or standard skin-sparing mastectomy. A skin-sparing mastectomy preserves the breast skin but does not preserve the nipple. There are large series of skin-sparing mastectomies (SSM) that have been studied suggesting that results are likely similar to standard mastectomy techniques. However, as in NSM, no randomized comparative studies comparing SSM with standard mastectomy techniques have been carried out. At this time, there are no large studies of NSM followed for sufficient time to verify its ultimate safety. Because there are no studies to draw upon, surrogate information must be used to make a judgment as to its appropriate use.
Nipple-sparing mastectomy for cancer
Without comparative studies, investigators have focused on the risk of finding occult (not diagnosable by examination or imaging studies) cancer cells in the nipple in women undergoing mastectomy for cancer. There have in fact been at least 13 studies which have looked at the incidence of occult nipple involvement by carefully examining the nipple under the microscope after its removal for cancer. Each study has slightly different results but there is some general agreement as to what factors lead to an increase in risk of occult nipple involvement.
- Proximity of the cancer to the nipple: The closer the cancer is to the nipple the more likely cancer cells will be found in the nipple. Most investigators agree that at least 2 cm (a bit less than an inch) should separate the cancer from the nipple. Some investigators think that a 4cm distance is safer and utilize this distance in their recommendations.
- Tumor size: As tumors increase in size, whether invasive or non-invasive (DCIS), the incidence of occult nipple involvement increases. Investigators differ on whether 3 or 4 cm should be the cutoff.
- Lymph node involvement: A definite risk factor but not as significant as (1) or (2).
- Multicentricity (cancer in more than one breast quadrant): This factor was not examined by all studies but was significant in those where it was studied.
Nipple-sparing mastectomy for risk-reduction (prophylactic)
Women undergo risk-reduction mastectomy for a variety of reasons including:
- Test positive for a mutation in the BRCA 1/2 genes.
- Strong family history of breast cancer without a positive genetic test.
- Women undergoing mastectomy for cancer and wish to reduce their risk in the opposite breast.
The issue in performing NSM for risk reduction centers around the milk ducts which exist in the nipple and the understandable concern that these ducts might serve as a source of new breast cancers. There are little in the way of actual studies which can support or deny that cancers actually arise in the ducts of the nipple. However, if one looks in the scientific literature, it will be difficult to find any studies which deal specifically with the risk of forming cancers in the nipple. (We are not speaking here about Paget's disease, which is cancer that has spread to the nipple from an underlying site in the breast.) Because cancers originating in the nipple have not been reported in the cancer literature, it seems reasonable to conclude that cancer originating in the nipple is rare or at the least, unusual. The low risk of nipple cancers may be at least partially explained by examining the actual anatomic origin of breast cancer. From very scholarly studies carried out in the 1970's, it has been discovered that virtually all breast cancers begin not in the large milk ducts similar to the ones found in the nipple but in the small microscopic ducts and milk-producing areas of the breast (lobules). A study publish by our group in 2008 in the Annals of Surgical Oncology examined this very question. We studied the nipple anatomy in patients undergoing mastectomy in which the nipple was removed. Our study found that the small ducts and lobules in which breast cancer arises were rare in the nipple. In the very few cases in which lobules were found, there were few in number and found only at the junction of the nipple with the underlying breast tissue and not near the tip of the nipple. From this study it seemed reasonable to conclude that because the anatomic structures needed to form a breast cancer were rare in the nipple, that cancer originating in the nipple should also be rare.
Surgical complications related to nipple-sparing surgery are not unusual. The ability to get oxygen to the remaining breast skin is related to blood supply. The blood supply to the nipple and areola is particularly tenuous following NSM. Necrosis (tissue death) of the nipple-areola has been noted in virtually all reported series. It appears to vary from a high near 20% to a low of 2-3%. Many factors likely account for the differences including experience of the surgical team, choice of incision, breast size (increase risk in larger breasts) and on how effectively breast tissue is removed from behind the nipple and areola. In some circumstances, necrosis can occur to only the most superficial layers of the skin and complete healing usually occurs within a few weeks. Some surgeons feel the need to intentionally retain breast tissue behind the nipple and areola while others feel that nothing short of an attempt to remove all visible breast tissue is appropriate. It should be noted however, that intentionally retaining breast tissue behind the nipple could be problematic particularly in patients carrying a BRCA 1/2 genetic mutation. Patients electing to undergo NSM should also note that in almost all instances, the nipple will have little to no sensation. It is not unusual for some patients note a return of sensation to the breast skin but few report a return of anything but the most minimal sensation in the nipple.
Nipple-sparing mastectomy is currently being performed at high-volume breast centers throughout the country. It would be fair to say that it is still investigational. However, we do believe that it is a procedure that warrants serious consideration when mastectomy is needed to treat cancer or desired for risk reduction. In the cancer setting, strict selection criteria should be followed at all times (as outlined above) in order to minimize the risk of recurrent cancer in the nipple. Cancers greater than 2cm from the nipple, less than 4cm in size can be considered. Axillary node status and multicentricity should be considered on a case-by-case basis. In the risk reduction setting, it is our feeling that there is minimal risk to retaining the nipple as long as great care is taken to remove all visible breast tissue from beneath the nipple. Coring of the nipple (removing tissue from within the nipple itself) should be considered in appropriate cases.
Alan Stolier, M.D.