CD31

CD31 (PECAM‑1) is a highly sensitive and specific endothelial marker, showing membranous staining and serving as a key stain for confirming vascular origin. It highlights both small and large vessels and assists in identifying vascular tumours, evaluating vascular invasion, and assessing tumour micro vessel density. CD31 is expressed not only in endothelial cells but also in platelets, monocytes, neutrophils, and some T cells, so granular membranous staining in macrophages can cause an incorrect diagnosis. Endothelial cells act as an internal positive control, and CD31 remains the most reliable endothelial stain in routine diagnostic practice (1).

Recommended Controls

Criteria for acceptable staining is a membranous staining pattern. Recommendation to include a haemangioma, tonsil/liver or appendix. The antibody strongly labels endothelial and plasma cells; expected staining is membranous. Tonsil endothelial and plasma cells positive while squamous epithelial cells will be negative. In liver, the hepatocytes will be negative but the sinusoidal endothelial cells will have a positive staining reaction from mild to very strong.

Expected staining pattern

Haemangioma

Liver

Disclaimer

These methods are intended as a guide only. Laboratories that wish to implement these methods should perform internal validation/verification prior to use. The RCPAQAP does not make any claim or warranty for the accuracy or performance of these methods.