MKI67 and neuroendocrine carcinoma: Postoperative histopathological and immunohistochemical analysis confirmed the diagnosis, revealing a poorly differentiated adenocarcinoma component (CK8/18(+), CDX2(+), C-erB-2(3+)) and a highly aggressive NEC component (Synaptophysin(+), CD56(+), Ki-67 (~40%)), indicating significant proliferative activity.