Histological staining for Vegfr3 (Fig EV1B) and for the lymphatic markers Prox1 and Lyve1 confirmed the inhibitory effect of BO‐110 in tumor‐driven neolymphangiogenesis at the cutaneous melanomas (Fig 1D) or at distal organs (see lungs in Fig EV1C) of Vegfr3Luc‐GEMM mice. Here, FLT4 is linked to neoplasm.