KIT and leiomyosarcoma: Consistent with previous reports in veterinary medicine (50), leiomyosarcomas included in the present study were always CD117 negative, a finding that further supports the role of CD117 as a diagnostic marker to differentiate leiomyosarcomas (CD117 negative) from GISTs (CD117 positive) (29) in dogs and in some human GIST cases (56).