CALCA and Merkel cell skin cancer: On immunohistochemical studies, MCC cells express both epithelial markers (AE1/AE3, CAM 5.2, pancytokeratin, epithelial membrane antigen, and Ber-EP4) and also neuroendocrine markers (chromogranin, synaptophysin, calcitonin, vasoactive intestinal peptide, and somatostatin receptor).