P4HA2 and oral cavity squamous cell carcinoma: Prolyl-4-hydroxylases catalyse the formation of 4-hydroxyproline, which is essential for collagen triple helix formation and fibre stabilisation.18 Increased P4HA2 expression has been detected in many solid tumours, including oral cavity squamous cell carcinoma,19 papillary thyroid cancer,20 and invasive breast carcinoma (IBC).21 Interestingly, P4HA2 is differentially expressed between normal breast tissue and IBC.22,23 However, to the best of our knowledge, no previous study has addressed the role of P4HA2 in DCIS progression and its prognostic impact.