Extrapulmonary neuroendocrine carcinomas (EP-NECs) are aggressive malignancies characterized by the expression of neuroendocrine (NE) markers, including chromogranin A, synaptophysin, and the neuron cell adhesion molecule, as well as a high proliferative index (Ki-67 > 55%). This evidence concerns the gene MKI67 and neuroendocrine carcinoma.