DIAPH3 and neoplasm: mDia2 was mainly expressed in the tumor stroma, in particular in cells adjacent to the activin A‐secreting tumor cells, which are most likely fibroblasts (Fig 4H), suggesting involvement of mDia2 in the pro‐tumorigenic effect of activin A. Furthermore, mDia2 co‐localized with the vascular endothelial cell marker cell MECA32, but not with the lymphatic endothelial cell marker LYVE1 in tumor sections, demonstrating that blood vessel endothelial cells in these tumors are also mDia2‐positive (Fig 4H).