CD31 and αSMA co-staining. Representative images of pericytes (αSMA, violet) that are not associated with blood vessels (CD31, brown) in: A 3 week MFP, B 4 week MFP, and C 5 week SC tumours. Several blood vessels are highlighted with black arrows; blue staining represents cell nuclei. D shows that pericytes are exclusively associated with blood vessels in healthy liver control tissue. Scale bars represent 200 μm.