The typical patient is a young adult dog (usually less than 2 years of age) with a round eroded growth somewhere on the front half of its body.

What Might this Growth be?

The good news is that the patient is probably too young to have a serious malignancy; still, one wants to be certain. The ringworm fungus can produce some raised round reactions called “kerions” which can look similar. The chances, are, however, that the growth in question is a “histiocytoma,” a common benign tumor which will eventually go away by itself.

The histiocytoma is a tumor originating from what is called a “Langerhans cell.” This cell lives in the skin and serves as part of the immune system by processing incoming antigens and presenting them to other immunologic cells. The histiocyotoma is especially common in Labrador retrievers, Staffordshire terriers, Boxers, and Dachshunds. It is not related to the malignant process called “histiocytosis.”

Finding Out For Sure:

Most of the time the tumor is small enough for easy removal and the diagnosis comes up on the biopsy report, confirming that the tumor is benign and will not grow back. If the tumor is in a location where removal is not easy (such as the middle of the ear flap or dangerously close to the eye) there are two other options: biopsy of a small piece of growth or cytology exam.

Biopsy may require sedation depending on the location of the growth. Sometimes a local anesthetic is enough. A small piece of tissue is snipped off and sent to the lab for analysis. In a few days we will know for sure exactly what the growth is.

Less costly but also less accurately, cells can be withdrawn from the lesion by a needle or simply collected from the tumor surface by pressing a microscope slide to the tumor surface. This omits the ability to see the architecture of the tissue and just the cells are available for examination. This may be enough for the lab to confirm the identity of the growth in question.

What to do with a Histiocytoma

On the average, a histiocytoma undergoes regression by itself within three months. This process may be itchy or may lead to minor infection. Removal of the histiocytoma is the fastest routine to resolution but, since they do go away on their own, leaving the growth along is reasonable (as long as we know for sure it is a histiocytoma). Topical therapy with a product containing DMSO and a cortisone derivative is helpful in controlling symptoms of irritation.