Just breathe. Finding a lump on your dog is scary, but don't panic! Any veterinarian will be quick to warn you to check out any lumps or bumps that pop up on your dog to rule out skin cancer; fortunately, not every new bump means cancer.
Is it a small, round, raised pink bump? Did it seem to appear almost overnight? Is the surface hairless and smooth, like a little button?
If you answered yes to these questions, it could be what’s known as a histiocytoma. Unfortunately, to the naked eye, button-like histiocytomas can’t be definitively distinguished from other types of bumps, so you should still see your veterinarian anytime you notice a new lump or bump on your dog.
A histiocytoma is one of the diagnoses you hope for when you find a bump on your dog. Knowing all about its appearance and lifespan will help you be prepared for what comes next.
What is a Histiocytoma in Dogs?
A little vocabulary lesson to start, though tumors are often associated with cancer, they are actually just growths that can be either benign (noncancerous) or malignant (cancerous). Veterinary pathologists have a way of naming tumors that make them all sound scary, but fortunately not all tumors are necessarily bad. Histiocytomas are one of those non-cancerous tumors. They typically don’t cause a lot of damage, and they don’t spread to other areas of the body.
Histiocytomas get their name because they originate from histiocytes, which are immune cells that live in the skin. The skin is a busy organ that undertakes many jobs on a daily basis. One of those jobs is the constant sampling of the environment for things like microbes, irritants, and allergens. Certain cells, known as Langerhans cells, are responsible for sampling environmental proteins and presenting them to the immune system to decide if they are friends or foes. Sometimes those Langerhans cells become overly zealous at reproducing and create small, red, raised button tumors known as histiocytomas.
Fortunately, a normal immune system quickly recognizes the overgrowth of Langerhans cells as bad and starts to take care of the tumor on its own. This means most histiocytomas only have a lifespan of a couple of months and don’t require further treatment.
Age and Breed Factors
Histiocytomas can pop up on any dog, no matter the age, breed, or genetic makeup, but as with most types of tumors, they have their own special preferences.
Age for Dog Histiocytomas
Dogs under three years of age are most affected by histiocytomas. This is likely because their immune system is still in development mode, and there can be some ups and downs as it works out the kinks.
Breeds Prone to Button Tumors
There do seem to be genetic factors related to the occurrence of histiocytomas, though we don’t completely understand what those factors could be. Breeds that show up more commonly with histiocytomas include:
Dachshunds
Staffordshire Terriers
Visual Identification of Histiocytomas in Dogs
Describing a histiocytoma as a small, pink bump isn’t good enough, so let’s talk about what histiocytomas typically look like during their lifetime.
Initial Phase (Week 1-2)
Your first glimpse of a histiocytoma will likely be a small red or pink bump that you run across while petting your pup. It will likely be under a centimeter (about the width of a pencil eraser) in diameter and have a smooth surface.
Growth Phase (Week 2-4)
Histiocytomas tend to grow very quickly, so that initial bump you noticed will likely increase in size over the course of about a month. Most stay under four centimeters in diameter, but some can get bigger.
Ulceration Phase (Week 4-8)
Histiocytomas may be benign, but that doesn’t mean they can’t cause your dog some trouble. As the tumor grows, it can be irritating, leading your dog to lick or chew on it, potentially causing bleeding and ulceration.
Regression Phase (Week 8-12)
The body tries to make short work of histiocytomas, typically siccing the immune system on it within a few weeks. Within a couple of months of noticing it, you should start to see the tumor progressively getting smaller, with most disappearing by about three months.
Common Locations of Histiocytomas in Dogs
Histiocytomas in dogs are typically loners, they don’t form in groups, and they prefer the front half of the body. The head, mainly the ears, lips, and nose, are by far the most preferred sites for dog histiocytomas. The front legs and paws are also common spots for them, but keep in mind that histiocytomas in dogs can show up anywhere.
Dog Histiocytoma Treatment
In most cases, your dog’s body will take care of histiocytomas in time, but that doesn’t mean you shouldn’t get your veterinarian involved. Once you have a definitive histiocytoma diagnosis, most vets will recommend the watch-and-wait approach, meaning you’ll monitor the bump at home while the immune system does its work.
It’s not time to sit back and relax, though. Instead, you’ll want to keep a close eye on the area to make sure the tumor isn’t growing or changing rapidly. You’ll also want to keep your dog from bothering it, which can prolong healing time. A light wrap or an e-collar may be necessary.
If your dog’s histiocytoma is especially irritating, your vet may recommend removal. This can be done surgically or by using cryotherapy to freeze it off. Most of the time this is reserved for those that become ulcerated and bleed a lot.
When That Pink Bump Needs Veterinary Attention
I can’t stress this enough: have every new lump or bump checked out by your veterinarian, even if you’re sure it’s a histiocytoma or other benign growth. None of us possess cytological vision, so what may outwardly appear as a non-cancerous bump may actually be something worse.
You’ll especially want to get your vet involved if the bump grows very rapidly or changes shape, color, or texture.
Your vet will get a proper diagnosis by taking a sample of the bump either using a needle or a biopsy. They can then look at the cellular makeup under a microscope to determine what type of tumor your dog is dealing with. Sometimes, samples will need to be sent off to a veterinary pathologist.
Mast cell tumors and even melanomas can take on the look of a histiocytoma, so it’s important to get a real diagnosis before you decide to wait and see what happens. Be prepared to answer questions about when the bump first showed up and if it has changed since you first noticed it.
Protecting Your Dog’s Health
Your first course of action with any lump or bump on your dog is to see your vet. It’s important to get a proper diagnosis, but we realize that vet visits do come with a cost. Tumors that don’t require treatment, like histiocytoma, will still come with a diagnostic bill, while tumors that need surgical removal +/- further treatment will be more costly. Embrace pet insurance for dogs can help cover those costs as it helps with unexpected or emergency bills.
Fine Needle Aspirate (FNA) can cost between $150 and $400.
A full surgical biopsy can run $400–$1,000.
If the histiocytoma becomes irritated or doesn't regress, surgical removal (excision) typically costs between $500 and $1,500.
You should never feel like you can’t afford to get your pup they care they need, so by getting them pet insurance while they’re young and healthy, you ensure that you can say “yes” to any care they might need. For additional coverage, consider adding an optional wellness plan that can help with the everyday veterinary costs associated with preventative care, like checkups, vaccinations, neutering, and even grooming. A good pet insurance plan means your only job is providing love and belly rubs while the experts handle the diagnosis and healing.
Histiocytomas in Dogs
If your dog is destined to develop a tumor on their skin, the best type you can hope for is a histiocytoma. These overgrowths of immune cells are typically taken care of by a dog’s immune system and cause little more than a couple of months of irritation.
Lumps and bumps are always scary, but a histiocytoma is the best-bump scenario. So now you can breathe freely again. All you have to do is follow your vet's instructions and be sure to give your pup some extra snuggles while their immune system does its job.