These associations give insight for the potential role of P4HA2 in DCIS behaviour through its action in enhancing stromal stiffness and collagen deposition/alignment, which in turn might help in tumour aggressiveness.43 Supporting this idea, our results showed that P4HA2 expression is higher in DCIS co-existing with invasive carcinoma than pure DCIS, and much higher in the stromal fibroblasts surrounding the invasive component. The gene discussed is P4HA2; the disease is invasive carcinoma.