FOLR2 and neoplasm: Sun et al. have investigated the use of folate–FITC as a fluorescent imaging agent for the visualisation of FRβ-expressing TAMs in head and neck squamous cell carcinoma.17 However, this technique appears to possess limited clinical value: TAMs penetrate tumours in a non-uniform manner and therefore targeting of folate–FITC to cells in the tumour microenvironment leads to heterogeneous fluorescence.