PGR and breast cancer: 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.