CGA and medullary thyroid gland carcinoma: Moreover, we validated the positive staining of CgA and Syn immunohistochemical markers, used in routine histopathological diagnostics, to confirm tumor categories of NENs (Fig. 1B, E, H, C, F, I) [47] and the positive staining of CgA and Calcitonin, specific immunohistochemical markers of MTC (Fig. 1M, N) [48].