In our case, the CCH/MMC and MTC demonstrated identical IHC profiles, expressing cytokeratins 7 and 19, CEA-M, and neuroendocrine markers CD56 (neural cell adhesion molecule, also expressed in the normal thyroid), chromogranin, synaptophysin, and PGP9.5 (protein gene product 9.5, neuroblastic and neural marker) with the notable exception of lack of calcitonin expression in the MTC. The gene discussed is SYP; the disease is medullary thyroid gland carcinoma.