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). This evidence concerns the gene KIT and gastrointestinal stromal tumor.