Histiocytoma in the dog could be a benign tumor. It is really an abnormal development in the skin of histiocytes (histiocytosis), a cell that is part of the immune system. The same condition in humans, Hashimoto-Pritzker disease, is also a Langerhans cell histiocytosis. Dog breeds that may be more vulnerable to this tumor include Bulldogs, Scottish Terriers, Greyhounds, Boxers, and Boston Terriers. Additionally they rarely exist in goats and cattle
Commonly histiocytomas are found in young dogs and appear as a small, solitary, hairless lump, although Shar Peis may be predisposed to multiple histiocytomas. They’re most often found on the head, neck, ears, and limbs, and are usually less than 2.5 cm in diameter.Ulceration of the mass is common. Medical diagnosis is created through cytology of the mass. Cytology reveals cells with clear to lightly basophilic cytoplasm and round or indented nuclei with fine chromatin and indistinct nucleoli.
Most histiocytomas may regress within two or three months.Surgical removal could possibly be required if the tumor does not regress or if it is expanding as well to a large size. Histiocytomas should not be helped by an intralesional injection of a corticosteroid, as remission relies on recognition of the tumour by the body’s immune system which is suppressed by steroids