Welcome, everyone, and thank you for participating in our virtual conference this year. I hope everybody's doing well and staying healthy. I am Bernard Segay and I am a professor of surgical oncology at Colorado State University, in Colorado, United States.

Today, we're gonna be talking about the tips and tricks for removing a tumour and basically understanding how to remove a tumour, the decision making and how to removing a tumour. So I was incredibly fortunate that when I was training, I had the great opportunity to be trained by Doctor Withrow, who is the, either the editor of the textbook, that we considered the the reference in oncology in vet medicine, or the latest edition, he is not the an editor anymore. He's retired, but his name.

Has on the on the front of the book. So I was very, very fortunate to train with him and I remember that we would be scrubbing for surgery and he would say, Bernard, we're gonna cut big, we're gonna cut wide, we're gonna cut deep and this dog is gonna live forever. And so this was the mentality for a lot of surgeries that we were doing.

In order to get the best results, and that meant that we would do some decent, Big surgeries that where the dogs ended up with a fairly decent defect in their bodies such as demonstrated here a hind limb of a dog. But that is not always necessary, and that is not always the case. And so the question then becomes, when we see a dog or a cat with a tumour, the question is, how am I going to remove this tumour, and in other words, how much margins do I need?

So for the purpose of today's talk, this will be most applicable for cutaneous and subcutaneous tumours, not that intracafeteria tumours are not important, but there are other factors in the decision making for intra cafeteria. And for today, we're gonna concentrate on the cutaneous and subcutaneous tumours in our decision making. So, as I said, some surgeries can be quite aggressive.

Here is an example of a dog where we have removed the bicep femoris. And this is another example of a dog that had a soft tissue sarcoma that required a full thickness body wall excision where we have removed ribs, and part of the abdominal wall as well, and we're just about to reconstruct with a latissimus dorsi muscle. And then there are other cases where we're going to be much less aggressive.

We're gonna be very conservative and we are going to in essence, pluck out the tumour as demonstrated here. So, before we go into the factors that will help us decide what margins we're going to take, I think it's important first to know that there are different doses of surgery, and the, this terminology is so that we can communicate very easily between all of us. And there are certainly shades of grey in between.

But nonetheless, this is a quick way to be able to understand what the surgery will be or, or has been. So 4 doses are intracapsular, marginal, wide, and radical. This illustrates the different levels of the or the different doses I should say.

So the picture on the Left shows that there is the tumour and as we're gonna talk about a little bit later on, there is a pseudo capsule around the tumour and we're gonna explain what that is. And so, intracapsular resection is where we break into the pseudo capsule and then we go and scoop the tumour out of its capsule. Marginal excision is where we go and we stay close to this, pseudo capsule.

Wide excision is, as the name implies, we go wider and by definition that typically is 2 to 3 centimetres away from the edge of the tumour, and we're gonna go over more details about the wide excision. And then the radical excision is the definition is where you remove the entire anatomic compartment from which the tumour is arising from. And therefore, as shown on the diagram on the right, the radical excision in this instance could be an amputation, so that is considered radical, and then for this particular tumour, and then the green circle shows the white excision, the blue circle shows the marginal excision.

When it comes to a tumour, and this is true even for a benign tumour, there are no tumours that should be removed with an intracapsular resection. If surgery is meant to be the only treatment and we are hoping for a a cure. And so even a benign tumour can grow back if we leave tumour cells behind.

And with the intracapsular resection, we have a very high likelihood of leaving tumour cells behind. So again, intracapsular not indicated if we are going to use surgery only, and this is true for both malignant and benign tumours. So now that we know that there are 4 doses of surgery, the one that we're going to choose.

Is going to be where we don't want to overtreat and so for the, the picture in this example, if this had been a benign tumour, we would have absolutely done a surgery that is much too big for the benign tumour. However, we don't want to undertreat because in many instances, it's not always true, but in many instances, if we undertreat, meaning that we leave tumour cells behind, Then it might either be impossible to come back and remove them, or very challenging, or at the very least it's going to provide more morbidity, it's going to inflict more morbidity to the patient and more cost to the owner as well. So what dose do I use of all the 4 doses that we've talked about?

This will depend on the tumour type, the tumour size, the tumour location, the stage of the patient, and the goals of the owners. And when we take all of these factors in consideration, this is how we're going to decide what is the dose that I will use. So when the tumour type is benign, then we know that benign, they don't infiltrate the local tissues and therefore, we are going to do a marginal excision.

So with a benign tumour, that's really the only factor that we need to consider is the type and then we can do marginal. If it's a malignant tumour, then we're going to, we're gonna have to consider other factors. When we remove a tumour, and particularly a malignant tumour, there can be 3 therapeutic goals, and these goals can be curative, palliative, or cytoreductive.

And depending on the goal that we set, that will decide the dose. And the goal, whether it's curative, palliative, or cytoreductive, will depend on the factors that we have just mentioned. And so I'm going to give some examples as to how these factors come into play.

So the therapeutic goal dictates the dose of surgery. So, if we want a curative intent surgery with a malignant tumour, most of them will require a wide or radical excision. If we want a palliative goal, then it can either be intracapsular or marginal.

Again, we don't use intracapsular very commonly, even in the palliative setting, but here again, because we're in the palliative setting, then intracapsular might be appropriate, and then cytoreductive, again, we would use intracapsular or marginal, but almost always we will favour marginal over intracapsular. So, we have talked about different factors, and one of them was the stage. In the stage, if there is presence of metastasis, then we are unlikely to be able to cure this patient anymore.

The disease has progressed to the point where it has spread, and it's unlikely that we have a cure. So in that instance, our goal is going to be palliative and as we've said before, with the palliative, that's gonna be either marginal or intracapsular. Size and location and owner's goals.

If it's a relatively large malignant tumour on an extremity, and so this is an example. So we have a a large malignant tumour on the extremity, and the owner refuses an amputation. But we have the possibility of adjuvant therapy, such as radiation therapy, then our goal is going to be cytoreductive.

And in that instance, then it's gonna be marginal or intracapsular. If we take the same dog and the same tumour, but these owners are fine with a radical excision, and the dog can tolerate it, then that will be a radical excision we would do an amputation. So this is a good example of where the owner's goals are very important in that setting because it will decide between a radical excision being an amputation or a marginal excision, which we could potentially follow with radiation therapy if the owners agree with this plan.

So we, we've talked about how we decide to, choose a dose of surgery, and again, the four doses were intracapsular, marginal, wide, and radical. The success of the surgery is not limited to the operation itself, but there are steps before the surgery that can help us achieve a better success. And this would be a biopsy, imaging, staging.

So I think that we have illustrated very well that you need to know what the tumour is in order to know how to treat it. Is it benign? Is it malignant?

Staging can make a big difference because if the tumour has metastasized, then there, is probably no point in doing a very aggressive surgery. And then imaging, very important as well in order to plan our surgery, particularly for tumours that are on the head, neck, pelvic area. There are other tumours if they're small, even if they may be malignant, if they're over the trunk, they're small, they're in the skin.

It might not require imaging, but if it's deeper, if it's fixed, if it's big, then we will want to have imaging. And then there are steps after surgery to ensure good success, postoperative care, good analgesia so our patient can recover well. And then we're gonna submit the sample.

We wanna know about our margins. We wanna know, did we get all of the tumour out and that the pathologist will be able to tell us if we were able to achieve a complete excision. When we approach the oncologic patient, we've talked about how it's important to know who the enemy is.

So, first step will be to do a biopsy, and then we will want to stage the patient, know if there is evidence of metastasis. And then we want to know the overall health of our patient, particularly if we plan to do a big surgery. Is this a dog or a cat that's got heart disease, kidney disease?

Can the patient undergo the treatments that we propose? So oftentimes we say that oncologic patients require TLC. In English, that can stand for tender loving care, but it's also a reminder that T can stand for tumour type, meaning what is the tumour, therefore referring to doing a biopsy before.

Location, referring to the stage, where else in the body can this tumour be? And then see condition of the patient, meaning overall health of our patient. When we are planning the treatment regimen, we absolutely need to involve the owners at, at the end of the day, they're the ones that are going to decide what the treatment plan will be, what can they afford, what they're willing to put their pet through, what they as an owner can tolerate.

In our treatment plan, we would like to minimise morbidity, and we would like to maximise quality of life, and I did not write it there, but we also, if we can maximise quantity of life. And sometimes, maximising quantity of life. Will mean a lot of morbidity, but if the prognosis is good, then we are willing to accept high morbidity in order to gain on the quantity of life.

So, we're gonna talk about the surgical principles. When we are doing a surgery for removing a tumour, we have said that there can be 3 goals when we remove a tumour. It can either be curative, palliative, or cytoreductive, and the first one that we are going to concentrate on is the curative surgery.

So surgery for a cure, we refer to this procedure, where the goal is to remove the entire tumour locally. And sometimes we're gonna call this the definitive surgery and this is to contrast with a biopsy, so a surgery to do a biopsy. That is not a curative surgery, whereas when we say, OK, I'm going for a cure, that means that I am planning to use surgery alone to hopefully cure the local disease.

And so here again, we have the example of a dog that's going through a body wall excision. So, as we go through the principles, there are some things that we need to remember that cancer is a contaminant and it can be seeded and it can be spread. We sometimes we'll hear the saying that a chance to cut is a chance to cure.

And it is very true, surgeons love to say that, but it's also a chance to make things worse, and it's very important as a surgical oncologist that we remember that we also have the potential to make things worse. We also have the saying that the first surgery is the best chance for a cure. And this is not always the case.

There are some cases where we do have the opportunity for a second surgery. But for some of these very aggressive surgeries, there is no second chance for being able to cure the patient with surgery. There might be radiation therapy, there might be chemotherapy, but as far as surgery goes, that might be the only chance that we have is the first surgery.

So this is a good example of a dog that had a tumour removed. We removed the bicep femoris, and so, if the clients do not want amputation, Then there's no coming back for this second surgery. There, we would not be able to do a second surgery and hope to remove all of the tumour cells left behind while we preserve function of the limb.

So if preservation of the limb is a goal, then this was the only surgery possible and there's no second surgery possibility for this dog. And, and we're gonna talk about the second surgery a little bit later on and explain why in some surgeries such as this one, the second surgery is not possible. In order to better appreciate why we do things a certain way, it's important to understand the anatomy of a tumour.

So here's the tumour, and at the periphery of the tumour, there is what we call the pseudo capsule. And the pseudo capsule is basically made of tumour cells that are being compressed by the cells dividing in the centre. As they divide and they grow, they push the peripheral tumour cells and they compress them against the normal tissue.

And the normal tissue too becomes compressed and becomes part of the pseudo capsule. And it's a pseudo capsule because as the name implies, it's not a true capsule, and we're gonna show you some histologic features of some of that pseudo capsule. Around the tumour and outside of the pseudocapsule, there is a reactive zone.

So oftentimes, the body will have a immune response, where there's inflammation around the tumour. And then, if a tumour cell escapes the tumour and goes into the reactive zone, that is called a satellite metastasis, if the tumour cells goes beyond the reactive zone and goes into the normal tissue that becomes a skip metastasis, if the tumour cell finds a lymphatic, And goes to a lymph node that is called a regional metastasis. And if the tumour cell eventually ends up in the blood circulation, And ends up in a different organ, which is often the lungs, and that is called a distant metastasis.

So there are really 4 levels of metastasis, satellite skip, these are local metastases, the regional lymph node, which is a regional metastasis, and then there's the distant metastasis. So we talked about the pseudo capsule, and this is a histologic slide that shows the compressed tissue. So we have the tumour and it shows the compressed tissue, the normal tissue and the tumour tissue that is being compressed and at surgery, that pseudocapsule can feel very, very discrete.

And can give the false security, sense of security that all of the tumour cells are contained within that capsule. And there are some cases where that might be true, but there are cases where that is not true. And at surgery, we do not know the difference because this is at the microscopic level.

And so this is a great example of the tumour edge infiltrating the normal tissue going beyond the pseudo capsule. And as I said, because this is at the microscopic level that surgery, you would not be able to tell if all of the tumour cells are within this pseudocapsule. Or if the tumour cells have been able to go through the pseudo capsule.

And so there are some tumour types where we assume that the tumour has been able to go through the its pseudo capsule into the normal tissues and for soft or for, yeah, soft tissue tumours that are cutaneous or subcutaneous, the two best examples are soft tissue sarcoma. And mast cell tumour. So because of that, because there are tumour cells that have gone beyond the edge of the tumour, then it's important to try to go beyond these pseudocas or these tentacles of cells and Because they're microscopic, we don't know where they are.

And so, in the example of the top right, we have the tumour and then there are tentacles of tumour cells that have been able to grow beyond the edge through the pseudocapsule. And we can see that if the surgeon were to do the margin at the blue line, then tumour cells would be left behind and therefore, there would be a very good chance that the tumour would grow back locally. Whereas if the surgeon cuts the tumour by using the green line, then all the tumour cells will have been removed and that is going to be a cure at the local site.

And that's what we want. Basically, we want to be outside of the tentacles, but because they're microscopic, we cannot see where they are, and that's why we have the wide excision. So #1 could represent a marginal excision, whereas #2 could represent a wide excision.

So, in the example at the bottom, if we have an incomplete excision, then we should see tumour cells at the edge and the pathologist should be able to tell us that this is an incomplete margin. Whereas if we go wide enough, then we'll have a complete excision, meaning no tumour cells at the edge. And just here it illustrates again that if you don't go wide enough, then you can leave tumour cells behind.

So therefore, because we don't see these tentacles, the recommendations and there is now more and more signs to justify these wide margins, although, the whole concept of how much margins to take is a evolving, field, sometimes highly controversial. But we're getting more and more data and as you can probably imagine, as the field evolves, it's also becoming more and more complex. And so, particularly with mast cell tumours and soft tissue sarcomas, we're learning more and more.

We're not gonna go into the details of these particular tumours in this particular, lecture. So for the time being, we're gonna give the general principles that what we recommend for the wide excision is 2 to 3 centimetres outside of the edge of the tumour, that is to capture those tentacles. So that's a quantity margin, 2 to 3 centimetres.

However, if you were to go 2 to 3 centimetres all the way around the tumour, at the deep margin for some of our patients, the particularly the smaller patients like cats and little dogs, that would be a complete or a full thickness body wall excision. And that is not done very commonly in spite of the fact that we remove very many malignant tumours. So the deep margin is instead of going for quantity, we go for quality.

And what that means is that We have learned that there are some tissue types that are natural barriers against cancer. These tissues are tissues that are vascular poor and collagen rich. And if a tissue has these particular features, so vascular, poor, collagen rich, then it's very hard, it's not impossible, but it's very hard for tumours to grow through these tissues and fascial planes, Most fascial plates, not every fascial plane, but most fascial planes, have these features, meaning vascular poor, collage and rich, and therefore they are a natural barrier against cancer.

So we use that to our advantage for the deep margin. So what we say is that at the deep margin, we're gonna remove the fascial layer that's under the tumour. And we're gonna remove it on block.

So as shown at the bottom right here, we are going to remove it on block. So that means we're not just going down to it and staying on top of it as shown on the left. We're gonna go down to it, cut through it, go underneath the fascial layer and then come back out.

So when we do a wide excision for malignant tumours, again, on the sides, we go for quantity, so 2 to 3 centimetre margins, and then for the deep margin, we go for a quality margin, and in most instances in the body that would be a fascial plane. We talked about imaging the tumour. It can be very important, because you wanna know what is involved.

Sometimes as shown on the picture, the tumour that you can feel is the tip of the iceberg, and then once you image it, you find out that the tumour has grown into the muscles. Again, I just said that that's not very common, but it does happen. So if you have a tumour that is not movable and palpation, if you have a big tumour or a tumour that's not movable or both, then this would absolutely qualify for having an image so that you can plan your surgery.

Otherwise, if you don't know that, then you would go wide and then you don't know that it's going to the muscles. So when you see the fascial plane, you would cut through the fascial plan and then you realise that you're cutting into the tumour. So knowing this, then you know that you go even wider, go deeper into the muscle so that you are away from the tumour.

So here we're showing how we have drawn at the edge of the tumour and then we're actually going to measure with a ruler all the way around so that there's no cheating, if I can say it this way. I think human nature is that you know, you may look at that as a surgeon, you go, oh, this is gonna be a big hole. Do I really wanna do this?

And so by measuring then you keep yourself honest to know that you're gonna go all the way around with the appropriate margins. And then for the deep margin, we are going to, for the fascial plane, some fascias are very intimate with their muscle and therefore you need to either remove the muscle itself or or do a partial thickness myectomy, . And if some fascial layers peel away from their muscle, and if that's the case, then You only need the fascial layer, you don't need the muscle itself.

But in this particular instance, we're on the lateral thigh, the fascial layer was the fascial lata, but caudally we got into the fascia of the bicep femoris, and so we have removed part of the bicep femoris, and this is what it looks like. And for this particular instance, dogs have an excellent function in spite of the fact that they don't have the bicep femoris. And then I'll go back one side.

So we are on the thigh area, it's a big defect. We can close by just bringing the edges back, but it's gonna have a lot of tension and it's a high motion area, so this is a very high risk for dehiscants. But what we can do is we can do what we call a bolster bandage to relieve the tension.

What that is is we put loops of sutures on either side of the incision. A lap sponge on top and then umbilical tape is passed like a shoelace, and then we tighten it so that the tension is taken at the level of the two rows of loops of sutures, and we relieve the tension on the primary incision, which is underneath the lap sponge. And so this is again the dog that had the big big excision on its thigh and we have used the The bolster bandage in order to relieve the tension.

At the incision site. Here's another example of a dog with a mast cell tumour. We're measuring our 3 centimetres and then we're gonna make it a little bit elliptical so that it closes well.

And then, very similar to the other one. But we are a little bit more distal than the other one, we are running into fascilata, and so the fascilata is going to be our deep margin. And then, same as the one before, we are over the thigh closest to the stifle, so lots of tension and therefore we're using the bolster bandage again.

So, as we're gonna go through the principles of the curative intense surgery, there are some guiding concepts that if you remember this, then all of the principles should make sense. Basically, remember that cancer is bad juju. It is bad stuff.

Remember that we can see tumour cells around. And therefore, when you touch a tumour or tumour cells, they can be on your gloves, it can be on your instruments, and when you go and touch some some other tissue with those instruments or gloves, then you have transferred or transplanted a cell in a different location. And that cell may not be able to survive, but it could also very well survive and that will create another tumour.

So, if you remember again, cancer is bad juju, then the concepts are gonna make sense. The best curative intent excision is where you never see the tumour grossly where you cut. So, I think you can appreciate from the diagrams that we showed just before that you wanna be away from the tumour.

You don't wanna see the tumour where you cut. So if you're cutting into tissues, and then at one point, you realise that does not look normal, that looks like tumour tissue. Then unfortunately, chances are you have touched it and you may have seated it.

So the best surgery is where you don't see the tumour at your excision, site. So, knowing that cancer is bad juju, you never want to puncture or rupture a tumour. Otherwise, tumour cells are gonna be oozing out.

We're therefore going to manipulate and handle the tumour with great care. We're gonna ligate the vascular supply before we transect it. That would be ideal, but I will be honest with you.

There are many instances where we cut the vessels before we find them, . And then there's a big debate whether you should do the artery or the vein first. To my knowledge, this debate has not been We don't know the answer whether you should do artery or vein.

There's an argument for each, in vet medicine, I think the argument, does not hold and therefore, I don't think it makes a difference in dogs or cats. If we use the example of an amputation. The obvious is that tumour cells go into circulation using the venous return to the rest of the body.

So with that idea, you should ligate the vein first so that you stop tumour cells from going to the rest of the body. In humans, while you are going to the artery, the artery can be pumping enough blood that it accumulates in the limb, and then you will lose that blood volume. In vet medicine.

And so therefore, the proponents of the artery are, is that you, the argument is that you do the artery first so that you don't lose that volume of blood and then because the artery has been ligated, then the pressure in the compartment on the, in the vessels drops to close to nothing and therefore, there's no, no force, no pressure to push the cells around. And again, to my knowledge, I've seen no data, clinical data to say whether that's true or not. I think in vet medicine, the argument is, does not apply because dogs and cats, particularly dogs, have a lot more collateral circulation in the limbs, for example, and therefore, whether you ligate artery or vein, it, it doesn't really matter, until you've ligated everything.

So, as far as the artery or the vein goes, whichever you find first, ligate it and then move on to the next one. We're gonna remove previous drainage or biopsy tracks. So if somebody's already done a surgery and put a drain in there or if somebody or yourself have done a biopsy, then that tract now is considered contaminated with tumour cells.

Remember, these tumour cells can have seeded through the draining tract or biopsy tract, so it has to be removed and it has to be removed on block with the tumour. It is best to use sharp dissection rather than blunt. The reason being that when you use blunt, one of the limb of the instrument goes towards the tumour and has a better chance of touching the tumour.

So, I still use a fair amount of blunt dissection, but I, I, I am very aware of the fact that one of the Arms of the instrument goes towards the tumour, so I try to be very careful and will favour sharp over blunt. Use monofilament suture material. This is maybe a little bit more theoretical.

There are some studies that show that tumour cells have an easier time sticking to multifilament, than monofilament. So monofilament from that perspective is better. But I would say, you know, more of a theoretical than a a clinical.

Argument. Therefore, if you have multifilament, sure, but if you can decide or pick, then go with monofilament. We're gonna isolate the tumour from the rest of the surgical wound, so particularly tumours that are, poking out of the skin, for example, and, I'm gonna move down to if the tumour is ulcerated, so we definitely don't wanna touch it with our gloves or instruments, so we're gonna cover it with a lap sponge so that tumour cells don't ooze out.

We're gonna irrigate as needed with sterile saline. This is really not for a tumour itself, but it is to keep the normal tissues healthy. And we're gonna remove the tumour with adequate margins, both lateral and deep, and so we've had a great discussion about, you know, the adequate margins.

Are they marginal? Are they wide? Are they radical?

And then what does it mean on the sides, on the lateral aspect, and on the deep aspect, remember, quantity versus quality margins. We're gonna use separate instruments and gloves and drapes for closure and for reconstructing if needed. And then also particularly, well, not particularly, but absolutely, if you're gonna remove another mass in the same dog under the same anaesthesia.

Please, please change your instruments and gloves. Even if you think that it's benign, don't take a chance. You would hate to take tumour cells from one side, with your gloves and instruments and then seed it in a different site.

So, it turns out that seeding, although, maybe I make it sound like it's very common. It is not. It seeding of tumour cells is not common, but if it is happening, if it does happen, the consequences can be extremely detrimental for the patient.

So this is an example of a dog that had a long carcinoma, and a long lobectomy was done, and then a few months later, the dog developed a bronchoalveolar carcinoma between the ribs and the rib site is exactly where the approach was done. So, I would make the argument that this is a very convincing this, that this is tumour cells that were seeded. There's no reason why you should have a bronchoalveolar carcinoma in your body wall.

And then to be at the exact exact intercostal space that the surgery was done, I think is a very, very convincing evidence that this is tumour cell seeding and now the dog, Needs to go through a very extensive body wall excision or radiation therapy, and so the consequences are very, very detrimental for this dog. So please change your instruments, gloves, if the drapes are dirty, put new drapes around, so that we don't see the tumour cells. Adhesions should be removed on block with the tumour.

Not, there, there are not very many examples in the cutaneous subcutaneous area. The best example is a splenic mass with omental adhesions. You would not peel the omentum away but rather cut the omentum so that the part that is stuck to the spleen comes out with it.

Avoid placing surgical drains or if a drain is necessary, place it such that it will not compromise a second surgery or radiation therapy. Remember, that drain is gonna be considered contaminated with tumour cells and so if your drain comes out 10 centimetres away from your primary incision, then having a second surgery might not be possible anymore because that has to be removed on block. Or if you're gonna do radiation therapy, that's gonna be part of the radiation therapy field.

And so now we have a much bigger field than if it wasn't for the drain. And so we rarely use drains in surgical oncology. We'll, we'll use them when we think that it's necessary, that it's in the best thing to do.

But oftentimes, you know, for over the trunk, for example, we'll just deal with the seroma and avoid having to place a drain. Lavage the wound bed or the body cavity. The reason why I put a question mark there is that, you know, people will say, well, if there are any tumour cells that have fallen out.

Into the surgical wound or bed, then I'm gonna flush them out. There's some signs to show that when tumour cells fall into the wound or into a body cavity, it literally takes, less than a minute, if I remember correctly, for this cell to have a strong, Adhesion may not be the right word, but a strong bond with the the peritoneum or the tissues and that lavaging will not remove them. So we don't rely on lavaging, but we do lavage again to keep the wound healthy or to to flush the body cavity.

You can identify the surgical wound with hemaclips and I'm gonna come back to that with when we're gonna talk about the cytoreductive surgery. So, we're gonna give you more details about that. And then if it's worth removing, it's worth submitting.

So please submit your samples to a pathologist so that they can confirm the diagnosis. If it's a tumour that you can grade to get a grade, and also know if your margins are complete or incomplete, and to help the pathologist, then we can mark the margins. So what we mean by that is to let the pathologist know exactly where the margins are.

And I have to say that pathologists are, even if you don't mark the margins, pathologists are incredibly amazing at keeping track of what is a surgical margin. But for big samples, they're gonna have to cut into the sample to make it fit into a slide. And then they're gonna use a microtome and so sometimes they could potentially lose track of, is this a surgical edge or it's an edge that I created because I had to cut into the tumour and I had to use a microtome.

So to help them, we can use these inks that are made for this particular purpose, so they're gonna withstand going into formalin and going through the HNE processing and all of the, you know, the formalin fix being in paraffin, so the whole processing. And so you can put ink at the edge of the sample where it is where you cut, and you can either use different colours or the same colour, And then this is to illustrate that when you have a big sample with pieces of muscles, please be careful where you're gonna ink. And so if you're not paying attention and you just threw the sample on the table, This muscle here is shown as being reflected.

So that this surface of the muscle should be against the tumour. And so if you don't pay attention, you're gonna put ink over here, but that was really not a surgical margin. The surgical margin is where the muscle is flipped back in this position, whereas it's this surface here that is the surgical margin.

So a little detail, but very important because if you were to put ink over here and there are tumour cells, then the pathologist is gonna say, well, you have an incomplete margin, but that really was not your true surgical margin. It was on the opposite side. And so just make sure that the sample is sitting as it was in situ.

But for most samples, this is a non-issue, like you don't even have to worry about that. And so here again, we show putting ink around and you can use different colours and you tell the pathologist yellow is deep and blue is gonna be medial or lateral and so on. Or you can use the same colour.

The argument for using the same colour is that as we're gonna talk about the second surgery in one slide, it doesn't matter where the dirty margin is or the incomplete margin is because once you have an incomplete margin, your instrument may have touched the tumour cell and now you kept going into the surgery and you may have seated it anywhere. So even if the pathologist tells you, oh, it's the dorsal aspect that's incomplete, you're gonna have to remove the entire surgical wound because the tumour cell may have been seeded. So, on the topic of 2nd surgery, it's when the first surgery had incomplete surgical margins, so a dirty margin.

Usually, it's when we leave microscopic disease behind, so you don't know where it is and you as the surgeon may have seated it or somebody else. Even when only one site was incomplete or dirty, the entire previous incision and bed with additional normal tissue must be excised. And if there were any draining sites that also has to be removed on block.

So, that I think you can now appreciate why some surgeries, you don't have a chance for a second surgery. So the example that I've been showing you where we remove the bicep femoris, if you go wider and deeper, you're not gonna have enough muscles to have a functional limb and so that is also true for orbitectomies and hemepelectomies and body wall excisions. If you have any complete margin with these surgeries, there's no going back.

This is, this is your one shot to get a complete excision. But for tumours that are either on the limbs. Or more so on the trunk, there might be an option for a second surgery.

And this is an example of where it was an incomplete excision over the trunk. We have the wound and then we're gonna go 3 centimetres around. And then importantly, we're also gonna go one fascial plane deeper.

So it's not just the sides around the tumour but also deep to the tumour that we also need to include. And if the person has already removed the fascial plane, the question is, is there another fascial plane or if not, is this a body wall excision? And then the question will be, is the morbidity worth it or should we do another type of treatment such as radiation therapy if appropriate?

But this is a good example of a second surgery. And on the topic of the second surgery, there are studies that showed that the second surgery can be highly successful for soft tissue sarcomas and mast cell tumours as well. So, that was the curative intense s or yeah, the curative intense surgery.

Now we're gonna talk about the cytoreductive surgery. So we're gonna skip the cytoreductive. So cytoreductive is when we know that we're gonna get an incomplete excision.

So we are planning to get an incomplete excision. It is the reason why we do that is that we have a tumour that is in a location that if you were to do a wide excision or maybe the wide excision is not possible and therefore it would be a radical excision. So a good example, tumour on the limb, it's malignant, so soft tissue sarcoma on the limb, it's relatively large, If we, there's no really option for a wide, so it's either amputation.

The owner says, no, I do not want an amputation. And so you say, OK, well, I can do a marginal excision. I'm gonna leave some tumour cells behind, but we're gonna follow with radiation therapy.

So, therefore, we're gonna do a cytoreductive surgery. So the goal is to downstage the disease, decrease the tumour burden, so such that the adjuvant therapy will have a better response. And the probably the best example is radiation therapy with mast cell tumour and soft tissue sarcoma.

So typically, in order to make the adjuvant therapy work better, you have to go down to microscopic levels. So, if you leave a chunk of tumour behind, if you say, well, I removed 90% of it grossly, Because you have some gross disease still left behind, radiation therapy is not necessarily gonna be better. So typically, you need to go down to microscopic level.

And then sometimes we do it and we don't really know if we are really making a difference. So it's unproven role in certain instances. A good example is MLO, which stands for multi multilobulate.

Osteochondrosarcoma. And These tumours, we don't know how well radiation therapy works. There's no good study or studies.

To really let us know what, what is it in the face of gross disease, what is it in the face of microscopic disease. But based on the general principle, we've done it, you know, we'll, we'll remove an MLO and marginal excision because the white excision is either gonna kill the patient or has unacceptable morbidity. And then we follow with radiation therapy and we hope for the best, even though we don't have studies to show whether or not this is really gonna make a big difference.

So if adjuvant therapy is radiation, then it's, it's good to mark the surgical bed so that you can identify it later to plan the radiation therapy field appropriately. If with the concept that when you do a surgery, there can be tumour cells anywhere in the wound. Then you know that you need to irradiate all of the surgical field and then a wider margin.

And so if the radiation oncologist fails to include all of the surgical field, then that can be a failure and have local recurrence. So to help the radiation oncologist know where the surgeon was, we're gonna put hemoclips, . Such that we help the radiation oncologist.

And then, depending on the type of radiation, sometimes the incision is gonna be oriented in a plane that's not best for the surgeon, but it's best for radiation therapy. So sometimes instead of going longitudinal, we're gonna go transverse and so on. But with the newer machines that has not been an issue anymore, the newer machines are able to conform the, the beams such that, we don't really run into that problem anymore.

So this is an example. We've removed the tumour and now we're putting our little hemaclips into the surgical wound and the idea is that we put them pretty much everywhere. So at the deepest level that the surgeon was, at the widest level, and a different depth.

And then we're gonna close it and then the idea is that the radiologist or the radiation oncologist is gonna take a radiograph or is gonna do an image and then where the all the hemaclips are is where the surgeon was and the radiation oncologist is gonna be able to readily see. Where was the surgical wound? And then be able to do a wider radiation field.

So we basically help the radiation oncologist and ultimately the patient by leaving these little hemoclips. And then finally, we're gonna talk about the last goal that we can have, which is palliative. So as the name palliative means is that we want to improve quality of life without necessarily prolonging the quantity of life.

So right here with palliative, our goal is to make the patient more comfortable. So goal is to improve quality of life without trying to prolong survival. Oftentimes it's a no-brainer, like you, you remove the tumour, it's low morbidity.

The tumour was causing a lot of problems, And the surgery is low morbidity, so you know that it's gonna be a win. But sometimes, you know, big tumour or it's a, it's a location that can be challenging to remove, sometimes you really have to consider what will be the morbidity of my surgery versus what am I gonna gain in terms of relief of pain or improved function, and you really have to consider which is the worst, which of the two is the worst evil. Is it the risks of the surgery or is it the pain of the tumour?

And like I said, more often than not, it's very straightforward. The surgery is gonna be the best thing to do and the, the, the quality of life is gonna be improved, but for some instances, you really have to think twice to know whether or not the surgery is really in the best interest. An example is removing osteosarcoma with an amputation.

Without chemotherapy, we don't prolong survival, but dogs, the majority of dogs do great with an amputation. They have an excellent quality of life. They recover relatively fast.

Most dogs within 2 weeks are up and running around, and so, we remove the pain and they can have an excellent quality of life for the remainder of their life. Sometimes we have a tumour and we think, well, what if I just remove part of the tumour? And I'm actually gonna leave some gross disease behind.

And an example of that is like a tumour of the hard palate. So we will see dogs with big tumours in the hard palate and the clients don't want a big surgery. But the tumour is ulcerated, and oftentimes the dogs are chewing on the tumour and that makes it bleed.

And so the question would be, well, what if I just like shave it off and remove the part that's in the mouth or the part that's being bitten when the dog is eating. And that usually is a very bad idea because you're gonna be cutting through the tumour tissue itself and you can end up with a lot of bleeding that you're not going to be able to control. Often it is not a vessel that you can find and ligate.

More often than not, it is this oozing throughout the entire surface that you've cut and Because these may not be normal vessels, there may not be the correct signals to stop the bleeding, and you can end up with a severe problem of losing a lot of blood volume and potentially, I've seen it, the dog losing so much blood that they're going to die. So this is not meant to scare you, but cutting into a tumour is more often than not a bad idea and something that should not be done or recommended. So this is it, .

I hope that you got a lot out of this lecture, and I will be very happy to answer questions at the appropriate time. Thank you very much.