TTF1 and neoplasm: Final diagnosis was confirmed by immunohistochemical (IHC) analysis which revealed that the tumor cells were positive for neuroendocrine markers, such as CD56, chromogranin A, synaptophysin, Cytokeratin (CK), and thyroid transcription factor (TTF-1) but negative for D2–40, CK20, CDX2, and HBME1 (Fig. 3).