NKX2-1 and carcinoid tumor: Immunohistochemical markers that were negative in all the carcinoid tumors in which they was used were Insulin (0%; 0/2), Cytokeratin 7 (Figure 3A) (0%; 0/1), Cytokeratin 20 (Figure 3B) (0%; 0/1), Calretinin (0%; 0/1), Calcitonin (0%; 0/1), Progesterone (0%; 0/1), Estrogen (0%; 1/1), Melan-A (0%; 1/1), Thyroid transcription factor-1 (0%; 0/1), Prostate specific antigen (0%; 0/1), Adrenocorticotropic hormone (0%; 0/1), Gastrin (0%; 0/1), Motilin (0%; 0/1), and Neurotensin (0%; 0/1).