Upsizing Breast Implants Does Not Raise Mastectomy Flap Necrosis Risk

CancerNetwork® spoke with Lisa Cassileth, MD, FACS, chief executive officer and founder of The Practice Healthcare, about her recently published retrospective study on 499 breast reconstructions performed at her private practice. The study compared outcomes between patients who received implants larger than their mastectomy specimen size (the upsize group, n = 361) and those who received smaller implants (the downsize group, n = 138) during direct-to-implant (DTI) reconstruction following nipple-sparing mastectomy. Cassileth’s team found that mastectomy skin flap necrosis (MSFN) rates were non-significantly lower in the upsize group (3.59%) than in the downsize group (4.35%), challenging a common clinical assumption that increasing implant size raises complication risk. Body mass index (BMI), rather than the numerical difference between implant and specimen size, emerged as the strongest predictor of MSFN.

Cassileth discussed the study’s implications for surgical decision-making, multidisciplinary treatment planning, and greater transparency in reporting surgeon-level outcomes.

CancerNetwork: What clinical assumptions or institutional protocols prompted you to evaluate whether implant upsizing impacts MSFN?

Cassilith: What prompted me was this frequent standard I’d hear, not just from other doctors but also from patients, that you can’t upsize the breast to a bigger implant because it wasn’t safe and would cause harm to the patient. The question is, is that true? If it is true, you shouldn’t be doing it, but if it’s not true, you should know that. There was this automatic, knee-jerk assumption that doctors would have to place a tissue expander or a smaller implant because it was dangerous to upsize the patient. If that wasn’t true, why would they think that, and how could we correct that line of thinking? We set out to reflect what we were seeing clinically, which was whether it was a danger to patients. Our result was that, strangely, not only was it not a danger to patients, but the patients undergoing upsizing had a lower complication rate than those undergoing a smaller implant relative to the mastectomy flap size.

What were your initial thoughts when you found that MSFN rates were lower in the upsized group compared with the downsized group, and how do you interpret these results?

Our first thought was that these are different patient populations. Looking at it, we thought, okay, perhaps it’s a thinner patient population…Let’s say your peak cancer diagnosis age is 55; our patients are a little younger than that because we also have a lot of prophylactic patients. Maybe over time, if they breastfed, they’ve lost volume, and you see that a lot in women as they age, especially after breastfeeding. They have a net loss of volume over time, especially if their weight stays similar, and they can even become more slender than they were before, with loose skin. The patient is like, “I used to be a C, now I’m a B. Can I just be my old size?” I don’t want to tell that patient no if the answer isn’t no. We thought, oh, this is because it’s a different group of patients. They’re lower BMI, they’ve kept their weight down, maybe they breastfed, and maybe this is just a healthier group. It turned out that although that was true, it wasn’t the driving principle. Patients at the same weight had less risk when they upsized vs downsized. We [also] thought, maybe it’s overall breast size. Now, it is true that the bigger the breast, the greater the complication rate. There’s simply more surface area, more square centimeters of tissue, so there’s more exposed trauma to the body, and some complications do go up, seroma especially. Seroma is a complication caused by damage to blood or lymphatic channels, from the overall trauma and surface area inside the breast. After we corrected for BMI and breast size, what we found was that it was more than just that.

I don’t have a definitive answer for you, except that as a plastic surgeon, you want a hand-and-glove fit between the remaining breast skin and the implant. If a patient is complaining that they’re too loose, using something that fills it out is going to give a better hand-and-glove fit than forcing them into a smaller device and having it drape off them like a Shar-Pei. That isn’t success. Not only does it not look good, but the body doesn’t like folds and wrinkles because they affect blood flow. We just want it smooth and even, with direct blood flow everywhere. Not only does it look better, but it’s more anatomically correct for that patient. Now, when you take someone who has larger breasts and wants to downsize, not only would you have that additional injury, but you’d also have tissue that has to shrink to fit a smaller device. Maybe you’ll get some of that Shar-Pei [effect], or maybe you’re just asking the skin to retract under the weight of that heavier breast. Now, you’re asking the tissue to do more, and that increases the complication rate and the injury risk to the patient.

The multivariate analysis identified BMI, rather than the implant-to-specimen size discrepancy, as the key predictor of MSFN. How should reconstructive teams weigh patient BMI vs tissue tension when planning direct-to-implant cases?

Doctors reading this, and patients too, will already know it’s not as simple as looking at BMI or making a straight decision about whether to go up or down in size. It’s about looking at that patient on that day. There’s a huge variation in the quality of the mastectomy flap. The mastectomy flap is what’s left behind, the tissue and subcutaneous fat, after I’ve removed the breast. That plane isn’t easy to find. We’re asking general surgeons and the mastectomy surgeons to cut between the subcutaneous fat and the breast. If you think about it, in a fatty, larger breast, that plane is harder to find because you’re trying to find a plane between fat and fat. Often, I’m finding that plane starting from the inframammary crease, at the bottom of the breast, working up. By the time I get to the top, it’s fat on fat. It’s technically difficult for the general surgeon, breast surgeon, breast oncologist, or whoever performs the mastectomy.

The reconstructive team comes in and asks, “Can I upsize?” Well, it depends on how it looks. It’s not a knee-jerk answer that upsizing is wrong; that’s what we know from the study. I also wouldn’t say you have to upsize and that it’s automatically safer. I’d say you have to trust your gut in terms of looking at the quality of the skin and the quality of the mastectomy flap. There are now devices, like SPY PHI, where I can give the patient an indocyanine green (ICG) dye and look at the blood flow. Those measurements are much stronger predictors than BMI or absolute size.

Ultimately, it comes down to the surgeon choosing an implant for that patient on that day, and that’s what we need to trust: the surgeon’s judgment. If a surgeon tells their patient, “When I work with this general surgeon, I’m going to use a smaller size, take more skin off, and place a tissue expander,” that’s because they have experience with that surgeon. It’s not that they’re not capable of doing it; they’re telling the patient what’s safe for that patient and for that surgeon’s patients.

Why did the overall complication rates trend higher in the downsized group for secondary end points?

That was mostly because of what we talked about before. The downsized group tends to have larger breasts, so there’s more loose space, meaning you’re more likely to have less of a hand-and-glove fit and a bit of draping and extra space. You might have a patient whose breast extended out further, and now I’m putting in an implant that sits closer in. There’s loose skin in that area, which makes it more likely for fluid to collect. It can also make blood vessels in the area more likely to bleed post operatively. All these things are more likely to happen because we don’t have a good fit between the implant and the breast size.

MSFN can significantly delay systemic therapy or radiation. How do these findings impact multidisciplinary treatment planning when coordinating timing with medical and radiation oncologists?

MSFN is a huge, underrecognized complication within the patient community, and the physician community is also a bit unsure of what to do about it. Rates are high, so I’d urge more action on the part of plastic surgeons and patients to do their research on which surgeons have the lowest rate of mastectomy flap necrosis, as it can delay treatment. If you look across different centers, and even individual doctors within a center, what you’ll typically see, even at wonderful institutions like Memorial Sloan Kettering, MD Anderson, and the University of California Los Angeles, is that the lowest rate of major complications, including mastectomy flap necrosis, implant loss, and serious infection, is around 22% if you look at data published over the last 10 years. This is just one small piece of the puzzle in figuring out what causes these complications. We know it’s not about a bigger implant as long as it’s closed under no tension.

In a strange way, the larger implant that’s more appropriate for that patient could, in many cases, be the better choice, not the worse one. We also have to work out every other aspect of what we can do to lower this risk. We’ve brought our own rate down to 1.5%. Do we need hyperbaric [oxygen]? Is it more than just the implant? We’re starting to look at all the other factors to figure out how we get that rate down because patients don’t want a complication or an implant loss on top of chemotherapy and radiation. Honestly, even patients who aren’t having chemotherapy and radiation don’t want a complication, either. We don’t want anyone to be deformed. We want the surgery to be a single moment in the patient’s life, and then once they’re reconstructed, they move on. I don’t want to say forget it ever happened, but ideally, they have something long lasting that’s never had a problem since the day of surgery.

How critical is intraoperative perfusion mapping when deciding whether a skin flap can tolerate an upsized implant during a single-stage DTI procedure?

It’s very critical. Some of it is visual because the edge often gets abraded, but when you do the intraoperative mapping with the SPY PHI device, you’ll see a lack of flow along that edge. What we’re looking for is scores ideally over 20, if you imagine 100% as normal blood flow. There’s a breakup point around 25%. If it’s under that, there’s an 80% to 90% chance of ischemic, low-blood-flow, necrotic complications. If we can get that number up, you can sometimes trim the very bottom of the skin, and you might not see the problem until you map it. If you trim the skin and then try to put in a big implant and can’t close it, you shouldn’t be doing that. It comes down to the surgeon’s best clinical judgment and assessment. If a patient comes to see me and says, “I used to be a DD, and I want to be bigger,” we make the final decision on the day of surgery once we can see that everything fits and the blood flow looks good. You only get that option if it’s appropriate for you at that time; otherwise, it could add risk to the surgery.

What is the primary takeaway that surgical oncologists and plastic surgeons need to understand from these findings?

Let’s stop saying, “Don’t do that, it increases risk.” I’d love for people to stop saying that because I don’t think it’s fair to patients. Many patients do want to upsize, and that’s okay. We should support our patients in doing so if it’s safe for that patient.

Reference

Cassileth LB, Killeen KL, York A, Rosen D. Does breast implant size larger than mastectomy specimen size increase the risk of flap necrosis? Aesthet Surg J Open Forum. 2026;8:ojag063. doi:10.1093/asjof/ojag063