For instance, Wang et al. [54] combined SERS imaging with a microfluidic chip for size-based isolation of CTCs (13–25 μm diameter) from leukocytes and red blood cells (<11 μm), as illustrated in Figure 2A. A mixture of breast cancer cell lines (SKBR3, MCF7 and MDA-MB-231) belonging to the three major breast tumor subgroups (luminal, HER2 and basal) were spiked in human blood and flowed through a sieving chip with 12 μm gaps. Here, ERBB2 is linked to breast cancer.