FLT1 and fibrosarcoma: This multiple kinase receptor expression may be a potential therapeutic target for UCs such as the use of sorafenib, which targets rapidly accelerated fibrosarcoma (RAF), VEGFR-1, VEGFR-2, VEGFR-3, PDGFR-β, and KIT leading to its direct anti-tumor effect and inhibition of angiogenesis, already observed in vivo experiments in nude mice with canine UCs [47].