Histiocytoma in Dogs

by | 02/23/2023

A histiocytoma is a benign or non-cancerous skin tumor that develops in some breeds of dogs. The tumor originates in the Langerhans cells, which are cells that play an important role in a dog’s immune system. Also referred to as dendritic cells or histiocytes, the Langerhans cells provide immunity to the tissues that mostly come in contact with the dog skin’s surface and outer environment, like the stomach, lungs, intestines or nose.

Skin Tumor (Histiocytoma) in Dogs

When the reproductive mechanism of a dog’s histiocytes, which usually regulates on its own, is somehow not functioning correctly, it can result in a histiocytoma. It’s unknown why this can happen in one dog and not another, so there is no way they can be prevented. Histiocytomas are also called button tumors because they resemble a button. Histiocytomas are a raised spot on the skin that has the look of a hairless and bright red lump.

Seeing them for the first time can be alarming to a dog owner because they can appear suddenly. Imagine bathing your dog one night and seeing nothing, and then seeing a large, red, nasty-looking bump the next day. It’s usually one lump but, in the case of the Shar Pei breed, it may be several masses or lumps appearing at one time.

Owners are generally the ones who notice them because they don’t appear to bother dogs. Although an older dog may develop a histiocytoma, they’re most common in young dogs under the age of three. Young dogs usually develop them on the face or extremities, although, they can occur in any location.

Which Dogs are Susceptible?

Because histiocytoma is a common mass or tumor, it can develop in any dog breed. However, they are more common in certain breeds. Some dog breeds that are typically predisposed to histiocytoma include:

  • Boxers
  • Bulldogs
  • Labrador Retrievers
  • Greyhounds
  • Shar Pei
  • American Pit Bull Terriers
  • Scottish Terriers
  • American Staffordshire
  • Boston Terriers
Breeds At Increased Risk
Breed Odds Ratio 95% Confidence Limit Probability
Chinese Crested Dog 5.98 3.01 – 11.90 0.001
Boxer 4.53 4.19 – 4.88 0.001
Flat-Coated Retriever 4.22 2.77 – 6.43 0.001
Bull Terrier 3.98 2.98 – 5.22 0.001
American Pit Bull Terrier 3.32 2.74 – 4.02 0.001
Boston Terrier 3.23 2.70 – 3.86 0.001
English Cocker Spaniel 3.16 2.28 – 4.38 0.001
Jack Russell Terrier 3.09 2.47 – 3.86 0.001
English Bull Terrier 3.08 2.17 – 4.37 0.001
West Highland White Terrier 2.60 2.27 – 2.99 0.001
American Staffordshire Terrier 2.60 1.45 – 4.68 0.001
Italian Greyhound 2.58 1.44 – 4.62 0.001
Shar-Pei 2.10 1.73 – 2.55 0.001
Bulldog (English) 2.07 1.55 – 2.76 0.001
Miniature Pinscher 1.96 1.02 – 3.77 0.040
Whippet 1.94 1.14 – 3.32 0.013
Rottweiler 1.79 1.60 – 2.01 0.001
Dalmatian 1.75 1.45 – 2.13 0.001
Mastiff (English) 1.73 1.24 – 2.42 0.001
Labrador Retriever 1.27 1.18 – 1.36 0.001
Beagle 1.27 1.12 – 1.44 0.001

How is a Histiocytoma Diagnosed?

While there is no way to prevent histiocytomas from developing, dog breeders who own dogs predisposed to this problem may want to consider limitations in breeding these dogs.

If your dog suddenly develops a lump or you suspect the dog may have a histiocytoma, it’s important to see a veterinarian. The method of diagnosis may vary depending on the vet and the condition of the tumor. First, the vet will ask you for a complete history of your dog’s general health and a description of the symptoms. Once the vet has this information, he or she will probably use the following methods to diagnose a dog.

  • Physical Examination – This may include a complete blood panel, complete blood count, chemical blood profile, electrolyte panel and a urinalysis. Despite the dog possibly having a histiocytoma, these tests may still come back normal.
  • Cytological Examination – This involves taking a small sample of the cells with a fine-needle aspirate and examining them under a microscope to look at several variable-shaped and sized nuclei. This test may show a high level of white blood cells in the vertebrate immune system or the production status of the cells high.
  • Biopsy – The vet may choose to do a biopsy if he or she wants more specific information on the status of the cells. Biopsies also provide a more definitive diagnosis.

How to Treat Histiocytoma

The treatment for a histiocytoma will vary from vet to vet, but treatment is usually determined by the severity of the histiocytoma. Once the vet determines that it definitely is a histiocytoma, the vet may decide to start treatment or take a wait-and-see approach. If the vet does decide to initiate treatment, the two most common treatments are cryosurgery, which is a type of laser surgery, or surgical excision of the tumor.

If the vet chooses the wait-and-see option, the histiocytoma will often regress on its own in a few months. Once the vet gives you all the available options and his or her recommendation, you’ll be able to make a decision on which course to take. If the tumor doesn’t go away on its own in three months, surgical removal is usually recommended.

How to Care for a Dog with a Histiocytoma

The care a dog with histiocytoma needs depends on the dog and the location of the histiocytoma. In many cases, it may be in a location where the dog may not even be aware the tumor. If this is not the case and the dog is able to see the lump, it’s important not to allow the dog to scratch, lick or bite the tumor. These types of actions can cause infection, inflammation and bleeding.

If the dog’s histiocytoma has been surgically removed, you’ll need to keep the incision site dry and clean to prevent infection. It’s also important that the dog doesn’t scratch, lick, bite or rub the site or the surrounding area. The veterinarian will provide you with post-operative instructions on how to care for your dog after the surgery.

You may also be given a cone for the dog to wear over the head to prevent the dog from getting at the incision site until it’s properly healed. Any signs of broken stitches, bleeding, redness or swelling should be reported to the vet.

What to Do if You Suspect Histiocytoma

One of the first things that might make you suspect a histiocytoma is noticing a button or dome-shaped mass on the surface of the skin. Although rare, it may exhibit blistering, which can mean it’s ulcerated. It usually grows fast despite being non-painful. In most cases, there will be only one lump, and they’re usually found on the limbs, head or ear edges.

If you do suspect your dog has a histiocytoma, it’s best to make an appointment with the vet to either get a treatment plan going or to rule out a histiocytoma. We seldom enjoy taking our dog to the vet because it often results in high vet bills. Because histiocytomas usually dissolve on their own in a couple of months if not treated, many dog owners choose to not see a vet if they suspect a histiocytoma.

This can be a serious mistake. One reason it’s important to have your dog checked by your veterinarian if you suspect a histiocytoma is because there are other histiocytic disorders a dog can develop. These may not be histiocytomas and may be more aggressive and less benign. The treatment for these other disorders is different than for a histiocytoma.

If the dog has a malignant tumor and it’s not treated or incorrectly treated, it can make the situation worse. Examples of histiocytic disorders are cutaneous histiocytosis, histiocytic lymphoma, systemic histiocytosis and malignant histiocytosis. If you mistake one of these disorders for a benign histiocytoma and don’t get treatment for your dog, the disorder can get worse and become malignant. Despite these histiocytic disorders being in the family as histiocytomas, dogs who are predisposed to histiocytoma are not predisposed to histiocytic disorders.

We’ve often heard the old adage an ounce of prevention is worth a pound of cure. This can be used in terms of preventative care for your dog. Histiocytoma, like many other canine issues, can be determined in its early stage by checking your dog regularly while petting, grooming or playing with the dog.


UPenn School of Veterinary Medicine

National Center for Biotechnology Information