High CD31 expression is often found in tumor tissues by immunohistochemistry and associated with a poor prognosis among cancer patients (Basilio-de-Oliveira and Pannain 2015; Cao et al. 2018), but high CD31 secretion by tumor cells has rarely been analyzed by protein microarray or ELISA, as observed in this study. This evidence concerns the gene PECAM1 and neoplasm.