A Vet’s Perspective on Histiocytomas in Dogs

Four Minutes
Nov 13, 2023

Are you wondering what that red bump is on your dog’s face or paw? If it seems like the bump showed up overnight, it may be a dog histiocytoma. Let’s dive into what a histiocytoma is, what causes them, and what you should know about treating a histiocytoma on your dog.

What Is a Histiocytoma?

A histiocytoma is a common benign skin tumor that appears spontaneously. Most histiocytomas usually go away without treatment in under 3 months.¹ These bumps are typically less than 2.5 cm and can be found anywhere on the body. The most common areas pet parents find them are on a dog’s nose, ears, and paws.

There are similar diseases called histiocytoses that behave differently than a histiocytoma. Histiocytosis can look like cancer or dog acne. Histiocytomas are:

  • Button-like
  • Solitary
  • Red colored
  • Raised
  • Hairless
  • Pus-less

Young dogs between 1 year and 3 ½ years of age are more likely to develop histiocytomas. All dog breeds develop histiocytomas but they’re more common in pit bulls, retrievers, bulldogs, and boxers.

What Causes Histiocytomas In Dogs?

While there isn’t an exact known cause of histiocytomas, some vets believe that the bumps are caused by an immune response in dogs.¹,² These sorts of bumps develop in the region of the skin that has histiocyte cells.

Histiocytes are a part of a dog’s immune system, and these cells exist in many parts of their body, including the skin, liver, and lungs. Whether or not the immune response is to food allergies, dust, ticks, or other things on the skin hasn’t been proven yet.

Types of Histiocytosis

A solitary histiocytoma is very common and not a cause for alarm. There are histiocytomas, however, that start as one bump then become a larger, systemic problem. Some may even be life threatening, cancerous, or a sign of immunity dysfunction.¹

These uncommon diseases fall under the term “histiocytosis” and affect more than one part of the body¹:

  • Cutaneous histiocytosis: This is a rare disease that causes many raised or flat bumps to develop deep under the skin, including under the fat layer of the skin. This can cause major discomfort around the legs and hindquarters. It can also potentially spread to your dog’s face, making it difficult for your pup to see and breathe.
  • Systemic histiocytosis: Typically found in Bernese Mountain dogs, systemic histiocytosis causes multiple skin lesions to come and go, with each wave becoming more severe than the last. This can spread all over the body and to internal organs if left untreated.
  • Malignant histiocytosis: Also found in Bernese Mountain dogs, this histiocytosis is defined by how rapidly it spreads to other organs like the liver, lymph nodes, and lungs. Malignant forms of histiocytosis usually occur in dogs over 7 years of age. Sadly, this form of cancer can be terminal.

All three of these diseases typically require specialized treatment from your vet. If your dog’s histiocytoma symptoms don’t seem normal, it’s recommended to schedule an appointment as soon as you can.

Are Histiocytomas in Dogs Dangerous?

Thankfully, most histiocytomas are noncancerous and painless. Your dog’s bump may go away on its own within 2–3 months without treatment.¹ Surgical removal may be an option for pet parents who are concerned with the appearance of dog lumps and bumps or if it’s bothering their dog.

A potential threat to your dog’s health is a secondary infection, not the histiocytoma itself. Bacteria and other debris can get into a histiocytoma, causing an infection that could make your dog sick.

Watch your dog to see if they are scratching, biting, or licking the bump. This could be a sign that the histiocytoma is infected. Consider checking the bump to see if it’s open or warm to the touch, then calling your vet to schedule a time for a thorough exam.

How to Treat Histiocytomas in Dogs

While histiocytomas usually go away on their own, it may be a good idea to consult with your vet to make sure the red bump isn’t anything serious. Your vet may choose to excise the area with a needle and send a sample to a lab for a biopsy to rule out cancer.¹

Take special care of your dog’s bandages while you’re waiting on the results of the biopsy. You may be provided with a cone to keep your dog from scratching the area. Follow your vet’s wound-care instructions closely to avoid secondary infections.

Can I treat my dog’s histiocytomas at home?

The short answer is no. You shouldn’t attempt to pop or excise your dog’s histiocytoma at home. Doing so risks harming your dog by exposing the open wound to bacteria. It may seem gross, but do your best to leave the bump alone so it can heal on its own. Otherwise, let your vet remove it for you.

How Pet Insurance Can Help with Histiocytoma Costs

While dog histiocytomas tend to go away on their own and don’t pose any harm, you may want to consider reaching out to your vet so they can check for any infections and potential cancer risks.

If you have a MetLife Pet dog insurance policy, you may be able to avoid a trip to the vet entirely when you use the 24/7 vet chat feature in the app and ask about your dog’s suspected histiocytoma. Don’t have pet insurance? Learn more about how pet insurance works or get started with a free quote!

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Dr. Hunter Finn is an integrative veterinary expert first, and social media star second. America’s favorite veterinarian owns Pet Method in McKinney, Texas, where he cares for pets while prioritizing their emotional well-being. When he’s not at his clinic, he’s starring in viral videos on TikTok (2 million followers) and Instagram (500K followers) — where he’s been known to snuggle puppies and conquer the latest dance trends.

¹ “Tumors on the Skin in Dogs,” Merck Veterinary Manual

² “Benign Skin Masses of Dogs,” MSPCA Angell

³ May not be available in all states.

Delaware insurance company, headquartered at 11333 N Scottsdale Rd, Ste 160, Scottsdale, AZ 85254 or Metropolitan General Insurance Company (“MetGen”), a Rhode Island insurance company, headquartered at 700 Quaker Lane, Warwick, RI 02886. Coverage subject to restrictions, exclusions, and limitations. Application is subject to underwriting review. See policy or contact MetLife Pet Insurance Solutions LLC for details. MetLife Pet Insurance Solutions LLC is the policy administrator for this coverage. The entity may operate under an alternate, assumed, and/or fictitious name in certain jurisdictions as approved, including MetLife Pet Insurance Services LLC (New York and Minnesota), MetLife Pet Insurance Solutions Agency LLC (Illinois).

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