TTF1 and medullary thyroid gland carcinoma: Positivity for cytokeratin, synaptophysin, chromogranin, TTF-1, S-100, and calcitonin focused the diagnosis on MTC, similar to other studies that have used immunohistochemistry to assess levels of calcitonin, CEA, synaptophysin, and chromogranin A, revealing positive results for TTF-1 and paired-box gene 8 (PAX8), while thyroglobulin (TG) was negative [13].