MKI67 and neoplasm: Referring to both the tumor morphology and Ki-67 index, the WHO incorporated a new subcategory of “well-differentiated high-grade tumors (i.e., G3 p-NETs)” into the well-differentiated p-NETs category in its 2017 Classification of the Tumors of Endocrine Organs [14], which was proven to be superior to the WHO 2010 criteria [20].