A histiocytoma is a non-cancerous cutaneous mass of dogs that arises from histiocytes within the skin. A cutaneous histiocytoma in dogs is common and extremely rare in cats. Cutaneous histiocytomas in dogs of all ages can occur, but they are much more common in dogs younger than 3 years of age and are the most common cutaneous tumors in dogs under a year of age. Any breed of dog can develop histiocytomas, however, purebred dogs are predisposed, in particular boxers and dachshunds.
What are the normal functions of the histiocyte cell?
Histiocytes are one of the most common cells in the immune system. They are a type of immune cell that functions to protect tissues from damage, disease, and infection.
What is a cutaneous histiocytoma in dogs?
Histiocytomas originate from Langerhans cells in the skin and may invade the surrounding structures in some cases. Histologically, a cutaneous histiocytoma is composed of sheets or nests of epithelioid cells derived from mononuclear infiltrating lymphoid cells or macrophages and often containing intermediate filaments (eosinophilic material). The cut surface of cutaneous histiocytomas usually reveals a dense, fibrous capsule with a mixed inflammatory infiltrate consisting of eosinophils and lymphocytes, including plasma cells. The cut surface also may contain hemosiderin-laden macrophages or giant cells.
How common are cutaneous histiocytomas?
Cutaneous histiocytomas are very common. They can occur at any age, but they are particularly prevalent in dogs that are three years old or younger. In fact, they are the most common cutaneous tumor in dogs that are one year old or younger, accounting for 89% of submitted samples for histopathology.
Another study, which analyzed 2,554 skin masses in dogs aged 0 to 12 months, found that 86.6% of those masses were diagnosed as histiocytomas.
They are known to occur in any breed, although purebred dogs, particularly boxers and dachshunds, show a higher predisposition.
What is the clinical appearance?
Cutaneous histiocytomas in dogs have a typical raised, rounded, pinkish-red appearance on the skin. They are often hairless and tend to be solitary and are usually smaller than 2 cm in diameter. When licking or self-traumatizing, the mass is likely to become ulcerated and infected which can lead to pain and discomfort for the dog.
How are cutaneous histiocytomas diagnosed?
A cutaneous histiocytoma in dogs is usually diagnosed based on physical examination and history. The cutaneous lesion can be aspirated for cytological evaluation or surgically removed for further testing if desired to make a definitive diagnosis. Special tests are often not required to make the diagnosis of cutaneous histiocytomas in dogs.
A surgical biopsy may be indicated, however, to differentiate benign cutaneous histiocytomas from other cutaneous masses and cancers that may need further workup and/or treatment.
What are the treatment options?
In most cases, cutaneous histiocytomas regress spontaneously without treatment within 1-2 months of being present without causing any clinical signs of illness. The cutaneous histiocytoma does not cause pain to the dog and no treatment is necessary for the majority of dogs. However, cutaneous histiocytomas can recur in some dogs after regression, and treatment with corticosteroids may be recommended to prevent cutaneous histiocytomas in dogs from recurring.
Surgical removal is recommended if it does not regress within 3 months, displays rapid and progressive growth, and/or becomes ulcerated, infected, and/or causes discomfort. Surgical removal is usually curative.
What is the prognosis for dogs with cutaneous histiocytomas?
Prognosis is excellent for solitary histiocytomas because many tumors regress within 1-3 months of diagnosis. Once regression begins, it can sometimes occur within days. If surgical removal is required, it is usually curative.
This article discussed cutaneous histiocytomas, which are common cutaneous masses in dogs. These masses arise from histiocytes within the skin and typically regress spontaneously. They are most commonly seen in dogs younger than 3 years of age and can be solitary or multiple. Treatment is not usually necessary but may be recommended for dogs that experience recurrent lesions. The prognosis is excellent for dogs with cutaneous histiocytomas. We hope this article helped you and please reach out to your veterinarian for any further questions or advice.