Internal Mammary Perforator Preserving Nipple-Sparing Mastectomy (IMP-NSM) to Reduce Ischemic Complications

CHAPTER 1

Hi, I'm Dr. Mardi Karin. I specialize in breast cancer surgery at Stanford University in California.

I've been studying over a hundred breast MRIs to evaluate the blood supply to the nipple areolar complex to determine what can be preserved during nipple-sparing mastectomy. I’m going to demonstrate my technique of preserving the dominant blood flow to the nipple areolar complex in the majority of patients during nipple-sparing mastectomy, which comes from a perforator through the pectoralis major muscle from the internal mammary vessels at the sternal border. I call this internal mammary perforator preserving nipple-sparing mastectomy or IMP-NSM.

I'm going show you all steps to the surgical technique. We start with reviewing the breast MRI if it has been done and evaluating the blood flow, which is a guide at surgery and can help with preservation. However, the same technique works even if the patient does not have a breast MRI. I'll be demonstrating that now.

CHAPTER 2

The first step is to review the breast MRI if they have it. The radiologist creates what's called a MIP image, which means maximal intensity projection, which averages multiple slices. It makes the skin look thicker but it also shows the blood supply very well. In this case, the MRI MIP image shows that to the right nipple, the dominant blood flow comes from this perforator from the internal mammary vessels, which you can see here. And the perforator comes up through the pectoralis major and courses up to get the closest of any blood vessels to the nipple. So I call that “IMP dominant” blood supply. In her, there's actually a second perforator. So this probably runs in the subcutaneous tissue. It actually even supplies this lateral breast, which is a little more unusual. Typically the IMP will course up and also supply the nipple area. So she definitely has a dominant internal mammary perforator blood supply to the nipple areolar complex because this is the main blood vessel and extends the closest to the nipple area.

On the left side, we see the IMP coming out of the pectoralis and then branching. And this again clearly, from the internal mammary perforators, extends the closest to the nipple areolar complex. So we describe that as internal mammary perforator IMP-dominant blood supply to the nipple. This is her cancer here in the right breast. And then down at the bottom are the MRI image choices and one of the little thumbnails says MIP or MIP image that are reformats created by the radiologist - and they can be rotated. The image is just not quite as bright but that can be adjusted for.

Still you clearly see the internal mammary vessels and you can also see the main blood supply to the nipple, which is here coming from that internal mammary perforator. That’s her cancer over there. So our radiologist typically will have a MIP reconstruction option that can be selected in the standard thumbnails shown, but if not, it can be easily created by the radiologist with clicking on a button because it's a standard reformat.

CHAPTER 3

This is the patient. She’s been marked by the plastic surgeon for either an IMF scar or a radial scar, whichever is needed. In her case because her cancer on the right is located near the inframammary fold, we're going to do an IMF scar. So the first step is to mark the intercostal spaces. This is the sternal notch so I mark that, and then the next one to mark is going to be the 2nd and 3rd intercostal spaces which I mark right at the sternal border and extending laterally. I usually mark the 4th intercostal space, which often is the location of the blood vessel to the breast tissue, but sometimes there's also a branch coming anteriorly there to the mastectomy flap. And then a dotted line about a centimeter laterally, and this ends up being the zone where we find the main internal mammary perforator: Typically at this 3rd or sometimes at the 2nd intercostal space. It’s typically right superior to the line that is marked by the Plastic Surgeon for the superior edge of the breast tissue.

Marking the intercostal spaces where we see the internal mammary perforator, similar to the other side, this is the 2nd, the 3rd, and the 4th intercostal space. I try to put this mark right at the sternal border as a guide and then a dotted line about one centimeter lateral to the sternal border. The Internal mammary perforator, or IMP, will usually perforate the pectoralis muscle right along this line, usually just superior to where the superior edge of the breast tissue is marked. That’s why it can be preserved, because it usually perforates there.

CHAPTER 4

Her breast MRI shows that the cancer is close to the skin right at the inframammary fold. After removing the skin over the cancer where it was close to the skin, then I'm going mark with a suture the inferior margin of the cancer at the mastectomy inferior margin.

CHAPTER 5

Now injecting tumescence, to the edges of the breast tissue. I’m showing you where the tumescence infusion cannula is - It's about in the subcutaneous tissue over the glandular breast tissue. And it's important to go just to the edge of the line marking the border of the breast tissue and do not go past the sternal border because that creates too much hydro-dissection over the sternum. Now the infusion cannula is up to the mark at the superior edge of the breast tissue. Actually, there's the tip of the infusion cannula and it's right in the sub-Q and it has a blunt tip. This tumescence is a very dilute solution of epinephrine by diluting 1% lidocaine with epinephrine approximately 25 cc in 250 cc of normal saline. Usually injecting about 150 cc – 200 cc on each side, and I do not inject behind the nipple areolar complex.

CHAPTER 6

You start to see the tumescence there, which is clear fluid. There was no tumescence here. It helps the pectoralis fascia separate posteriorly because It diffuses all the way down to the pec fascia, which I'm removing now. With an IMF scar, do this part of the operation early.

With an IMF scar, I do whatever dissection is easy, posteriorly first, it helps to be able to pull down the breast tissue to do the anterior dissection and many people feel it makes the anterior dissection easier. Now the plan is to raise the anterior mastectomy flap up to the nipple area.

What I'm doing is feeling the thickness of the mastectomy flap, which is about 5 mm. Then divide these Cooper's ligaments up by the subcutaneous tissue. Particularly in the beginning and throughout, whenever the plane is not obvious, just gentle spreading identifies those Cooper's ligaments. Now we're going to look at doing the dissection towards the nipple. We’ll look at the color of the nipple which is nice and pink beforehand, and my dissection is up almost to the areolar border here. I'm going to do that on both sides of the areolar border. I've already done the dissection on the medial side in the area of the areolar border, and now I'm going do the lateral side also.

CHAPTER 7

So now this part here starts to be the ductal tissue going to the nipple. So this is important. Once we get up to the under surface of the nipple area -and almost at the nipple, then I spread on both sides to expose all of the ducts going up to the nipple. No cautery in this region. It usually separates quite easily actually. Grab the tissue that's going to the under surface of the nipple with an Allis clamp. I’m advancing the Allis to be closer because we're going to get up to the dermis of the nipple. This is the under surface of the dermis of the nipple, there and then this tissue going to the nipple is cut. There's the actual undersurface of the dermis of the nipple. I cut with Metz because it cuts very easily if you're not cutting the dermis. I find it's easier to put a suture first on the anterior margin of the tissue behind the nipple. We lift up on that and then take the biopsy somewhere between 5 mm to 7 mm of length removed, and this goes for frozen section for the tissue behind the nipple. This is the area of the dermis underneath the nipple. You can see inside the nipple there. And then this is subdermal in the nipple areolar complex because usually the breast tissue comes very close to the dermis in this area.

Now we want to get back into the subcutaneous plane on both sides, which is really important. Before I divide the rest of the tissue, I'm going to wait for this frozen section because right now I have all my landmarks easy to see and if I need to remove it, I know where that biopsy was done. And we're going to let the perfusion of the nipple restore itself, while I'm going dissect in another region now.

CHAPTER 8

Removing the Pectoralis Fascia, to near the superior-medial border of the mastectomy dissection. [No Dialogue.]

CHAPTER 9

As we get closer to our marks at the sternal border, dissect more carefully and look for branches of the internal mammary perforator vessels or the associated anterior cutaneous nerves that often perforate nearby.

There’s a little vein right there, and the artery's usually in the same bundle and it's perforating at this intercostal space. And if we look on the outside, it's right about here near the dotted line on the skin. You can see some branching. This looks like the nerve, which is the anterior cutaneous branch of the intercostal nerve, right there - which is clearly supplying this, the mastectomy flap right here which is about 4-5 mm in thickness.

You can see another one probably perforating right here. It's not necessary to dissect it out completely as long as we preserve it, but you can see that there's always a nice layer of fatty tissue around the IMP. So we can remove all the breast tissue - in fact, here is the breast tissue. Here are some little branches going to the breast tissue that are going to be divided while preserving the internal mammary perforators here to the mastectomy flap. And here is another little branch, which is a little branch of the vein, coursing over this direction.

This is the breast tissue, which we have here taking off of the pectoralis. We're going to divide this with cautery, with removing the pectorals fascia here. These are the branches of the IMP coming up here: vein and the artery is probably underneath there, and we showed the nerve before. So we know that that it's preserved there. There's usually some little branches coming to the breast tissue that will bleed a little bit. That's the breast tissue so the tissue around it can easily be divided with electrocautery and if we look closely, we can see that there's just a fatty plane, which is adjacent to the breast tissue that separates very easily posteriorly.

CHAPTER 10

This is the PEC block. This is the pectoralis muscle and the serratus coming up to the area of the pectoralis muscle. Inject under the fascia of the serratus plane, just under the pectoralis muscle. As you look superiorly, you start to see more of the pec minor muscle, which I can see way in there. But wherever the fascia is exposed, aspirate first and then inject.

This is the PECs 2 block between pec minor and serratus. Normally we're injecting with 0.25% Marcaine with epi because it diffuses well. Here you can see the fascial plane under the pectoralis muscle - I lift it away from the chest wall either with a pickup or my hand and retract so that we're never injecting near the chest wall. The local anesthetic is injected. Here actually is pectoralis minor, and then this is pectoralis major. There’s actually a few fibers of pectoralis minor, and this is pectoralis major so under this fascial plane and pointing away from the chest wall, this is a PECs 1 block.

CHAPTER 11

I just demonstrated all of the key steps to preserve the important internal mammary perforator blood flow to the nipple areolar complex during nipple-sparing mastectomy. I showed that it could be accomplished easily through an inframammary fold incision, which is often the preferred incision for cosmetics. However, we adjust the incision based on the oncologic situation and the preference of the plastic surgeon.

Also, we inject tumescence, which facilitates hydro-dissection and separation of the fatty tissue from the glandular breast tissue. Also, I demonstrated the technique of doing a biopsy of the tissue directly behind the nipple. I showed how the undersurface of the dermis of the nipple is exposed. Then typically I prefer to divide the tissue with Metzenbaum scissors because it's difficult to cut the dermis with the Metzenbaum scissors so it usually preserves the dermis. And you could see where all the ductal tissue was removed, and then the suture placed, and it was sent to pathology.The next step is to complete the anterior mastectomy flap dissection after the posterior dissection is done and most of the breast tissue and pectoral fascia is already removed posteriorly.

Finally, I usually do near the end of the dissection the exposure of the internal mammary perforator (IMP) vessels when we have maximum visibility on both sides. With gentle, very careful dissection in that area, we could see the internal mammary perforating vessels, where they come through the pectoralis, and they were preserved and left on the mastectomy subcutaneous flap. It was very easy to see the subcutaneous tissue that we usually see around those vessels and still remove all of the breast tissue and pectoralis fascia.

At the conclusion of the procedure, the nipple areolar complex appeared well perfused. Also in this procedure, there was very nice exposure of the lateral cutaneous branch of the intercostal nerve (visible in Chapter 8, 12:50 – 13:02 min), which sometimes I preserve if the Plastics and Reconstructive surgeon is planning to do nerve reinnervation, and those have been grafted to the under surface of the nipple to restore nipple sensation in some of our patients with promising early results.