Report Von Willebrand's Disease Histiocytosis is a cancer in which histiocytes proliferate rapidly and invade a wide variety of tissues . Histiocytes are a type of white blood cell called macrophages which ordinarily form part of the dog's immune system. Their proper role is to engulf bacteria and other material which should not be present in the body and dispose of it. It is unclear how closely related the two types are. It is possible that they are different forms of the same disease.
Malignant histiocytosis is the more aggressive form and usually leads to death in a matter of weeks.
It frequently involves the spleen, liver, and lymph nodes. It can also invade other tissues including the lungs and skin. Systemic histiocytosis can have episodes that come and go with varying severity. It invades the skin and peripheral lymph nodes in almost every case but also involves other tissues particularly in later stages of the disease. The appearance of the histiocytes themselves also differs between the two forms.