PECAM1 and neoplasm: CD31 was detected in immersion fixed paraffin sections of tumor tissues using anti-CD31 rabbit polyclonal antibodies (ab28364; Abcam, Cambridge, UK) at 10 μg/ml overnight at 4°C followed by incubation with goat anti-rabbit IgG H&L HRP Polymer Antibody (ab205718; Abcam, Cambridge, UK).