Cluster 596: neuroendocrine cell small carcinoma histology cancer tumors prostate features acinar Cluster 696: differentiated neuroendocrine poorly grade carcinoid tumor pancreatic tumors moderately carcinoma Cluster 1121: small prostate carcinoma cell neuroendocrine consistent pathological finding histologic diagnosis Cluster 2001: neuroendocrine prostate adenocarcinoma differentiation features cell histologically small confirmed cytologically