Histiocytic Sarcoma (HS) is currently a marker test, or "pre-test" and cannot currently specifically identify the gene(s) mutation(s) for HS. Histiocytic Sarcoma (HS) is an aggressive, lethal form of cancer and is a major cause of death for predisposed breeds. It is a cancer of the cells responsible for immune functions. Age of onset reported is 6.5 years, and the progression of disease is usually rapid. To date, there is no effective treatment, and the disease outcome is fatal. HS is likely to have a multifactorial mode of inheritance, so currently any genetic test offers an estimate of risk only. There is ongoing research for this disease/marker test.