Olfactomedin 4 (OLFM4) is a glycoprotein that has been suggested to act as a tumour suppressor [20] and has recently been identified in specific granules of approximately 25 per cent of circulating human neutrophils [21], where it inhibits the activation of several granular proteases, including cathepsin C, neutrophil elastase, cathepsin G and proteinase 3 (PR3). Here, PRTN3 is linked to neoplasm.