Table 1. WHO Classification: Comparison to WHO 2010 and 2017.

WHO 2010	Mitoses/10 HPF*	Ki-67 Index*	WHO 2017	Mitoses/10 HPF*	Ki-67 Index*
Well-differentiated NENs			Well-differentiated NENs
NET grade 1	< 2	< 3	NET grade 1	< 2	< 3
NET grade 2	2–20	3–20	NET grade 2	2–20	3–20
			NET grade 3	> 20	> 20
Poorly differentiated NENs			Poorly differentiated NENs
NEC (small-cell or large-cell), grade 3	> 20	> 20	NEC grade 3	> 20	> 20
			Small-cell type
			Large-cell type
MANEC			MiNEN*

^*MiNENs may have non-endocrine component other than adenocarcinoma, e.g., squamous cell carcinoma or acinar cell carcinoma. To qualify as MiNEN, each component must be at least 30%. HPF = high power fields, MANEC = mixed adenoneuroendocrine carcinoma, MiNEN = mixed endocrine non-endocrine neoplasm, NEC = neuroendocrine carcinoma, NEN = neuroendocrine neoplasm, NET = neuroendocrine tumor, WHO = World Health Organization