FLT4 and neoplasm: Furthermore, exosomal BCYRN1 significantly increased the WNT5A expression and the density of VEGR3 or LYVE‐1‐indicated lymphatic vessels in the footpad primary tumor tissues while treating with SAR131675 markedly attenuated the exosomal BCYRN1‐induced increase of lymphatic vessels (Figures 8C–8F), suggesting that blocking VEGFR3 inhibits exosomal BCYRN1‐mediated lymphangiogenesis of BCa in vivo.