SYP and Merkel cell skin cancer: A study of 56 MCC (47 primary tumors, 9 nodal metastases) and 50 control cases (basal cell carcinomas, basaloid squamous cell carcinomas, Bowen disease, sebaceous neoplasms, melanoma, and B-cell lymphomas, and 28 lymph node control cases that included metastatic neuroendocrine neoplasms, melanomas, squamous cell carcinomas, lymphomas, and adenocarcinomas), INSM1 was expressed in all 56 cases including primary and secondary tumors, while synaptophysin, CK20, and chromogranin were expressed in 96%, 92%, and 32% of MCC cases, respectively [72].