PECAM1 and primitive neuroectodermal tumor: The double immunofluoresence staining of CD90 (green) and CD31 (red) on pancreatic neuroendocrine tumor (PNET) showed that CD90 largely overlapped with CD31 (Figure S7 in S1 File), indicating that CD90 might be a promising marker for pancreatic neuroendocrine carcinoma.