SYP and Merkel cell skin cancer: Tumor cells in MCC typically express markers of neuroendocrine and epithelial differentiation, such as neuron-specific enolase (NSE), CD56, chromogranin A, synaptophysin, and low molecular weight cytokeratins (CK8, CK18, CK19, CK20), CAM 5.2, and AE1/AE3 [35,36,37].