CCL19 and metastatic malignant neoplasm: In vivo, it varies among tissue types and depends on local physiologic and pathologic conditions.52 It was measured at 0.1–1 μm s−1 in homeostatic conditions in rabbit ears,34 and up to fivefold increases were reported upon contact inflammation in mice.41,53,54 In one of the very few human studies, IF in brain tumors was consistently of the order of 10 μm s−1 and could increase up to 50 μm s−1 in patients with metastatic cancer.55 The experimental Péclet numbers measured here for CCL19 correspond to homeostatic velocities.