MYLK and breast cancer: The transcellular route of migration has initially been recognized for leukocytes,28 especially in the brain microvasculature.29, 30 As for tumour cells, the transcellular route of migration has only been described in the diapedesis of breast cancer cells through an in vitro vascular network 31 or through human umbilical cord endothelial cells (HUVECs).32 During this process an actomyosin transcellular circumferential invasion array is formed, regulated by myosin light chain kinase (MLCK) and myosin II regulatory light chain (RLC) phosphorylation.