Histiocytomas in dogs

Cutaneous histiocytomas in dogs are benign skin tumors that can grow rapidly but then spontaneously regress and resolve without medical intervention.


A cutaneous histiocytoma is a proliferation of cells involved with the immune system called Langerhans cells. Histiocytomas are skin tumors that are raised and hairless and may be flesh-colored, pink, or red. They often look like a small button on the skin.

These benign tumors that are most commonly found in dogs less than 6 years old. They initially grow rapidly over a period of one to four weeks. Then they often remain the same size until they spontaneously regress and disappear a few months later.

Histiocytomas are often readily diagnosed by fine needle aspirate and cytology. Because they can appear similar to mast cell tumors, it is important to complete this diagnostic to confirm the type of lesion. If the lesion is a histiocytoma, no further intervention is necessary. It will regress and resolve on its own.

(What if it’s not a histiocytoma? What else could it be? Click here.)

Most dogs leave histiocytomas alone and don’t bother them. But if your dog licks or scratches at a histiocytoma, it can become ulcerated and infected. Having your dog wear an Elizabethan collar (the “cone of shame”) and keeping the skin nodule clean and dry will often resolve the infection. A short course of an antibiotic may also be prescribed by your veterinarian. 

Histiocytomas that continue to become infected or are not regressing on their own may need to be surgically removed by your veterinarian. This is typically a minor and straightforward procedure but it does require general anesthesia. Your dog will likely go home the same day that the procedure is performed.

For most dogs, the presence of a histiocytoma requires nothing more than monitoring until it resolves. It will often disappear almost as quickly as it initially appeared.