SYP and neuroendocrine carcinoma: By immunohistochemistry, 71% (9/13) of NEC were extensively (≥90% tumor cells) positive for synaptophysin (8/13, 62%) and/or chromogranin (4/13, 31%), with two others (SCNEC5 and ANEC1) showing patchy staining for both neuroendocrine markers (Figs. 1 and 2, Supplementary Table S2).