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Table 2 Classification and grading criteria for NEN (2019) [8]

From: Primary grade 2 neuroendocrine tumor of the ileal mesentery: a case report

Terminology Differentiation Grade Mitotic rate (mitoses/10 HPF) Ki-67 index
NET G1 Well differentiated Low < 2 < 3%
NET G2 Intermediate 2–20 3–20%
NET G3 High > 20 > 20%
NEC small-cell type (SCNEC) Poorly differentiated High > 20 > 20%
NEC large-cell type (LCNEC) > 20 > 20%
MiNEN Well or poorly differentiated Variable Variable Variable