PanNET : Grading

The histologic grading of pancreatic neuroendocrine tumors (PanNETs) is based on the proliferative activity. By definition,

• Grade 1 tumors have <2 mitoses/10 HPF or 2 sq.mm and Ki-67 index <3%.
• Grade 2 tumors have 2-20 mitoses/10 HPF and Ki-67 index between 3-20% (shown in this image)
• Grade 3 tumors have >20 mitoses/10 HPF and Ki-67 index >20% and usually <55%.

If the mitotic count and Ki-67 index are discordant, it is recommended to assign a higher grade.