Histiocytomas are a common skin growth observed in dogs. These growths originate from Langerhans cells, a type of immune cell found in the skin. It is important to understand that these growths are almost universally benign.
Understanding Histiocytomas
Histiocytomas typically present as small, raised, firm, and often hairless lumps on a dog’s skin. Their appearance can vary, sometimes becoming reddened or ulcerated on the surface. These growths are most frequently found on the head, ears, and limbs of affected animals.
Histiocytomas are particularly prevalent in young dogs, usually those under two years of age. While they can occur in dogs of any age, their incidence significantly decreases in older animals. These growths are essentially a proliferation of specialized immune cells.
Benign Versus Malignant Growths
The distinction between benign and malignant growths lies in their behavior and potential to spread. Benign growths are localized, grow slowly, and do not invade surrounding tissues or spread to distant parts of the body. Malignant growths, in contrast, are characterized by uncontrolled, rapid growth, the ability to invade nearby structures, and the potential to metastasize.
Histiocytomas are benign. They commonly undergo spontaneous regression, often disappearing on their own within two to three months without intervention. While exceedingly rare, a distinct and aggressive form known as malignant histiocytosis or histiocytic sarcoma exists, but it is a systemic disease originating from different cell lines and is not to be confused with the common benign cutaneous histiocytoma.
Diagnosis and Typical Management
Veterinarians typically diagnose histiocytomas through a combination of visual inspection and a procedure called fine needle aspiration (FNA). During FNA, a small needle is used to collect cells from the lump, which are then examined under a microscope in a process known as cytology. This cytological examination often reveals characteristic immune cells that confirm a histiocytoma diagnosis.
Due to their benign nature and tendency to self-resolve, the most common management approach for histiocytomas is a “wait and see” strategy. Surgical removal may be considered if the histiocytoma is causing discomfort, bleeding, or is located in an area where it is frequently irritated. Surgery may also be recommended if the diagnosis is uncertain or if the growth does not regress as expected.
When to Seek Veterinary Advice
While histiocytomas are generally harmless, any new lump or bump on a dog should always be examined by a veterinarian. This initial evaluation ensures an accurate diagnosis and rules out other, more concerning types of growths.
Prompt veterinary attention is warranted if the lump grows rapidly, becomes ulcerated or bleeds, appears painful to the touch, or does not show signs of regression within a few weeks. If the dog is older, or if the lump has an unusual appearance for a typical histiocytoma, a veterinary visit is also important for further assessment.