Histiocytoma – everyone’s favorite tumor for dogs

I know, the words “favorite” and “tumor” in the same sentence is a little weird. Hear me out…

Imagine a lump showing up on your dog’s leg. It’s big. It’s nasty looking. Sometimes they bleed. You’re freaked, so you take your dog to your veterinarian to see what it is. You’re envisioning surgery for removal of the growth, or worse, this thing spreading and shortening your dog’s life. Will he need chemo? Is this going to keep growing? Will he get more? Will we have to amputate the leg? Sometimes our imagination gets a little carried away, and if you start reading crazy things on the web – forget about it!

Would you ever expect a tumor to go away on its own? Is that even possible???

This is not a joke! That gross looking tumor will seriously be gone in 3 months. This is one problem that you can literally ignore and it will go away. This is why the histiocytoma (pronounced HIS-tee-oh-si-TO-ma) is everyone’s favorite tumor! Here’s the scoop:

The tumors are made of cells that live in the skin, but function as part of the immune system, called histiocytes. (They may also be called Langerhans cells if you want to have a fun fact for a party.) A group of these goes a little crazy, no one knows why, and forms a mass. It can be small like a pea, or 2+ inches in diameter. They typically show up on the legs and feet, but I’ve seen them on the trunk as well. These tumors are typically found on young dogs, under the age of two. However, my 8-year-old dog decided to get one, so anything is possible!

They can be pink and peaceful looking, or bleeding and “angry looking”. Therefore, your veterinarian cannot diagnose it just by looking. Sure, the age of the dog and location may make her think histiocytoma right away, but we need to confirm.bernese mountain dog

How does a veterinarian make sure it is in fact a histiocytoma? Easy! We take a syringe with a needle, like we use to give a vaccine, and stick it in the mass. We pull out some cells and look at them under the microscope. The good news is histiocytomas are pretty loose about giving up cells, unlike other tumors who do not give up any. So we’ll easily be able to tell in about 10 minutes if this mass is a histiocytoma. In rare cases, the veterinarian may get a lot of blood contamination, making it hard to see the histiocytoma cells. If your vet wants to send the microscope slide to a pathology specialist and have them look at it to make sure, that’s never a bad idea.

Once your veterinarian confirms microscopically the tumor on your dog is in fact a histiocytoma, we always love to share good news. Go home, ignore it, and it will go away in 2-3 months! Can’t be more benign than that!

Admit it….you now have a favorite tumor too!

Posted in General health.

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