Mast cell tumors, which is another mean one. So we probably all can recognize the granules we see. And I'll show you another cytology and that fun little lump on the dog, which could look like anything. So these guys are a wide variety. We're going to deal mostly with the cutaneous mast cell tumors. Remember, they can be other places, but this is a neoplastic proliferation of mast cells, obviously. With the cytokines that normal mast cells have, it's just that we have a whole bunch of them in one spot. And so those cytokines can ruin your day when they come out of those mast cells. It's histamine, it's heparin, it's proteases. And we have a lot of problems when these mast cells do the degranulation, when they release those cytokines that a normal single or maybe two mast cells would when you get stung by a bee. So again, older dogs 8 to 10 predisposition again is our poor boxers. We also see Bostons, Goldens, Labs. Again, there's a lot of breeds on this list and absolutely anybody can get it. This is a beagle I saw the other day. We also see it in our bully breeds. So English bulldogs, we'll see in pugs, we'll just see in shar peis. So kind of that list of dogs that has bad skin, they are more likely to develop mast cell tumors. And this usually presents as either cutaneous or subcutaneous mass, and they're really variable in appearance. You cannot point to a mass on a dog's skin and say ah, that's definitely not a mast cell tumor because they can look like anything. They are typically fur less. The two I'm going to show you in this presentation have fur on them. Okay? So even though they're typically furless. They really look like almost anything. And so they really need to be tested. And then, you know, they can occur anywhere in the body but limbs, lower abdomen, chest are really common sites. So to keep that in mind. And you can have extra cutaneous sites, but they're more uncommon. We will see them in like liver or that sort of thing with it with a whole different set of signs. But we're going to kind of focus on the cutaneous ones. One thing that will clue you in especially look a little bit harder is sometimes the owners will tell you a history of the mass swelling and shrinking and they're like, it was it was bigger the other day. It looks better. And that is a huge red flag with that as a mast cell tumor because it released some of that histamine and it and it swelled locally and then it didn't have any more histamine and it shrunk back down. So that should be a big red flag. And then clinically, though, oftentimes these are incidental. This is a mass you find when you're doing your physical exam, you're like, we should we should aspirate that. Like maybe it's all lipoma, but let's aspirate it and then you get a mast cell. But if they start to degranulate, then they sometimes come in for clinical signs. So you can see local edema. They can get itchy, they're red, they're angry. I don't know how well you can see in this picture. This is a beagle I had the other day with this mast cell that ruptured. If you look at the foot that has the obvious tumor on it, it doesn't look that big until you look at the other foot. This foot was actually really swollen in comparison to the other foot. And when you have bad enough mast cell, you can get systemic disease. So GI ulcerations are super common in these guys. And actually a study looked at a necropsy of dogs with mast cell tumors that didn't necessarily have GI signs and 50% better than 50% had GI ulcerations. So really, really common. You'll see delayed wound healing. And then you can get into the really scary times where you essentially start to work on anaphylaxis. So hypotension, you can get coagulopathies, these dogs can get absolutely critically ill. They'll come in looking like an anaphylactic reaction. 

Alright. So diagnostic again, cytology almost always does this for you, you can get this off a cytology so that's pretty handy. One thing you want to know is you should always, always, always please, if this is the one thing you remember from this always pre-treat your patient with Benadryl, give an IM injection of Benadryl prior to aspirating anything that you think could be a mast cell tumor. And since we just said anything can be a mast cell tumor it should be a lot of your patients that get a little Benadryl. Benadryl. Super safe, right? Super cheap. Let's give it. So we want to do fine needle aspiration, both of the mass and the regional lymph nodes. That's very important when we're talking about mast cell staging. We're going to do the routine blood work, really not generally going to see a lot of that. That's okay. We might think of doing abdominal ultrasound. We're going to check the spleen and liver. We're going to aspirate them if we're concerned. But that's all for staging. We certainly need the histopathology here, but it's more for grading. And then this is where mast cells again get confusing. So there's more than one grading scheme. The most common grading scheme you're going to see is a one through three grade. So one grade one mast cell being well differentiated and less aggressive behavior most of the time, Grade two in the middle, and then a grade three mast cell tumor being undifferentiated and tends to be very aggressive, more metastatic, more locally invasive. But I think just for funsies, there's more than one grading system and there's a lot of variability in how pathologists grade these. So again, lovely study that handed the same mast cell slides to a big group of pathologists and got different grading on these mast cells really frequently. So we want to grade them, but we also want to remember that that that is not a beginning and end. The mitotic index is really important with these guys, especially as a prognostic factor and we want to evaluate the margins. Histopathology histopathologically really important. Did we get all of that tumor, at least at that site? Okay. So histo is really important, but a lot of times you can do a fine needle aspirate and get this diagnosis. There's other testing out there. Again, all of this and please don't think you have to memorize this for NAVLE®, new, exciting, that we're getting a lot more information. And again, that will help us a lot more than this like grading scheme that we've been struggling with. Kit mutations might be the one to remember that is pretty up and coming because it also helps us know how to treat them. But there's a lot of different testing out there for these guys. If you ever see a question or somebody says, do a Buffy coat smear, that is no longer something we do to look at mast cells. So that would be looking at for peripheral mast cell tumors, you know, floating in the blood. And it's actually been shown that other diseases besides mast cell tumors are more likely to cause peripheral mast mast cells floating. So we don't look at Buffy smears or Buffy Coats anymore. 

All right. So treatment again, my fun Benadryl here. But treatment is surgical. We want to remove these guys. Okay. We do want, obviously, to pre-treat with Benadryl at the time of removal as well as famotadine. So an H1 blocker and an H2 blocker at the time that we're going to try to take these off. And sometimes we do pre treat with prednisone for up to a week as well, and that's to try to shrink down those margins a little bit to help us get clean margins, especially with a bigger tumor when we have a either high grade or non resectable tumor. So if you if you saw that beagle with that tumor on his leg, there's no way we get just that off, that whole leg has to come off. So that's not an option for the owner or it it's just not a surgical location or they're very high grade. Then we start adding in other therapy. So radiation therapy is used when we have resected a mass and either have dirty margins, meaning some of that tumor was left behind or we have a higher grade mast cell tumor, or just a little afraid we could have left some behind. So we use radiation there. Chemotherapy is used to delay metastasis and local recurrence. It will slow the nonsurgical mast cell tumors, but certainly not curative. Most common chemotherapy agents. There our CCNU. We do use prednisone, you know, continual, even post-surgical, vin blasting. I was always taught blast the mast as a nice little rhyme to remember one chemotherapy agent. But again, most of these are in the oncologists hands. Chemo is used basically when you think there's a high risk of metastasis. So even we have clean margins. If we have a high grade tumor that's when we're pulling out that chemotherapy or if we didn't get it all. And then again, don't worry too much about this other therapy. There's a lot of interesting up and coming things, new drugs on the market, new ways of treating things. Okay. This protein kinase inhibitor, the Stelfonta, which I'm not sure I'm pronouncing correctly, actually is injected into the mass itself in distal limbs, it's so cool. But there's a lot of interesting new things. If you have mast cell left behind, if you had gross disease, then you do want to keep these guys on long term H1 and H2 blockers. If you've got it all, they don't need to be. This is not something that, you know, if you're taking a mast cell off, they absolutely have to continue on. So I did have a case the other day. I thought we'd interrupt the chatting about to look at a case and just kind of quickly go through what what I think is a mast cell tumor. I actually don't know yet. 

But this is Wheeler who presented to me on emergency. He's a 13 year old whippet, and he had this mass that the owners describe, as always, kind of yucky, but they thought it was a lipoma. They're like, yeah, people even commented it's purple. It was never a lipoma. It was purple. And Wheeler did something that ruptured this mass on a Sunday because that's when masses rupture and you can see it is actively bleeding. My brave vet student here who's holding him so that I can take a picture is blocking the blood from hitting her scrubs. And we couldn't get this to stop. We try not to remove masses on emergency, but if you're going to keep bleeding, we don't get choices. So this is a really nasty tumor. I have a 13 year old dog with a grade four heart murmur that we now have to take this off and we don't get to stage, but we're going to go through how we did it anyway. What you could do with this mass is if we look kind of imagine my hands coming on either side and kind of lifting under, it's a dermal mass. I can just touch my fingers. I think I can get it off and close it, but it's going to be really tight. So for reference, head is still the same orientation as that first picture where it's towards the right of your screen, leg is down towards my cautery. Okay. And that will stay the same. We clip this up, you'll notice again there is hair on this mass, and it is still there when my tech clips it because I tell her please don't really touch it too much. Let's let's not make it angrier than it already is. We've obviously premedded both with benadryl and famotadine. Another thing to note is how angry this skin is. And this is before we have done anything, there was so much edema and swelling and bruising in the skin was the other reason I was really thinking mast cell. We did as much staging as we could, obviously, but for this guy on emergency, we just had to stop the bleeding. But we're going to go ahead and make an elliptical incision, which you can see we're starting to do here. We're dissecting a tissue plane down, lifting that off. I do not think I got lateral margins because there was, you know, very close there. But I had to be able to close it. So when we get that guy off, we have our nice elliptical incision there you can see sort of in the middle. I can turn on my laser pointer. Yeah, see if you guys can see that right There was one of our big vessels that was definitely our problem. We've got that tied off with another one over here. We did flush this off with saline, because again, I had kind of that gross fur. So we tried to clean up that wound bed and then we're going to close this big incision that's going to be tight. And you can see I'm using walking suture. So we're way back here in Deep Subcu and we're going to walk that forward. I'm going to put more tension on this happier side than this compromised side over here. And you'll see when we start walking it towards each other, you can see the dimples of the deep walking sutures. And then we've done a more subcutaneous, superficial line here and we're doing some interrupted dermal sutures. And then we finally get to our skin where we have no tension whatsoever. So I was pretty happy with how that closed. All this bruising and edema over here makes me pretty nervous for dehiscence, makes me pretty nervous for mast cell. But that was Wheeler. I thought we'd go through a quick how we remove those in the emergency, not quite as ideal of how we normally do it. So let's see. 

All right. So moving right along. Pearls of mast cell tumors. Grade is most important. But of course, grade is hard to get sometimes. But if you have a grade one or grade two, most times, if you can get it completely excised, that is an excellent prognosis. If you have one where you have a little bit of dirty margins or a little bit of cells left behind, if you do radiation on that area, it brings it back to an excellent prognosis. So that is a really nice thing. You have only a 5% recurrence rate. So this is one of those cancers that sometimes we get to talk about a cure with when we have the right grade. When you have a high grade, you have these high mitotic index really concerning for survival. So greater than five mitotic index, which you get from that histo has a three month survival versus less than five mitotic index has an 80 month survival. Huge, huge differences. And that's why getting that histopathology for the mitotic index is important. Dogs with bulldog and ancestry, so our bully breeds actually have a higher risk of mast cell tumors, but a bit more benign behavior. So you get them more frequently. They're more likely to be a grade one, you know, not aggressive form. And there's some association with where it is so we can see it on the muzzle of this dog. That is a poor prognosis. Nail bed, location, mucocutaneous junction are all poor, poorer prognosis. So sometimes we look at the location as well as some of the grading to help us determine. And then, you know, just things to remember. These guys like to bleed when you poke them. So in addition to the Benadryl, you have to warn the owners, sometimes these bleed. Sometimes we need to put pressure or bandages because oftentimes they end up with me on a Friday afternoon at five because now the leg is big and puffed up and it's bleeding and the owners are angry. So we at least need to warn them that they can bleed when you poke them. And if you find one, you need to look all over this dog for others. So, 10% at the time of diagnosis will have another mast cell somewhere else in their body. And a dog that develops mast cell tumor will have a 10 to 40% chance of developing one elsewhere. So even if we have a nice benign form, we think we cured it. That owner needs to be vigilant. We need to be vigilant in our exams where we're looking for new lumps in their lifetime. So something to really keep in mind, and this is the most common malignant skin tumor in dogs is not the most common skin tumor. It's the most common malignant skin tumor in dogs. We really do see a lot of these with our dogs. Alright.