In one example of this, Lee et al., conducted IF staining of the oestrogen receptor (OR) and progesterone receptor (PR) with an aim to discriminate OR and PR positive CTC subtypes; highly relevant in breast cancer diagnoses (Fig. 5B).122 Similarly, Shi et al. included single cell staining for HER2 on their valve controlled PDMS microfluidic chip. Here, ERBB2 is linked to breast cancer.