2017 World Health Organization (WHO) classification and grading of pancreatic neuroendocrine neoplasms (PanNENs)

* The Ki-67 proliferation index is based on the evaluation of ≥500 cells in areas of higher nuclear labelling (so-called hotspots). The mitotic index is based on the evaluation of mitoses in 50 high-power fields (0.2 mm² each) in areas of higher density, and is expressed as mitoses per 10 high-power fields (2.0 mm²). The final grade is determined based on whichever index (Ki-67 or mitotic) places the tumour in the highest grade category. For assessing Ki-67, casual visual estimation (eyeballing) is not recommended; manual counting using printed images is advocated.