SYP and neoplasm: Most tumor cells of the neuroendocrine component were immunoreactive for CAM.5.2, cytokeratin (CK) 7, CK AE1/AE3, synaptophysin, chromogranin A, parathormone, GATA3, and parafibromin (Fig. 4), whilst they were negative for thyroglobulin, TTF1, calcitonin, glucagon, and S100.