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.
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:
- Red colored
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.
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.
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.
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.