MKI67 and large cell neuroendocrine carcinoma: The histological features of LCNEC are as follows: (1) positivity for neuroendocrine markers, among which chromogranin A and synaptophysin are the most commonly identified; (2) a mitotic count exceeding 20/10 HPFs or a Ki67 index of over 20%; and (3) a specific NET pattern of an organoid structure, rosette formation, palisading, and trabecular arrangement, as well as prominent nuclei that are over three times the diameter of a lymphocyte.