MKI67 and metastatic neoplasm: Secondly, the SEER database lacked some vital information, such as tumor composition, pathological morphology, ki-67 index, mitotic count, immunohistochemical markers, metastatic tumor burden, and patient's general condition, which may also be related to the tumor heterogeneity and prognosis of MiNENs patients (Milione et al. 2018; Zhang et al. 2021b).