MKI67 and neoplasm: Grade 1 pNET a well differentiated tumor or low-grade tumor with mitotic rate < 2 mitoses/2 mm2 and Ki-67 index < 3%, Grade 2 pNET a well differentiated tumor or intermediate grade tumor with mitotic rate 2–20 mitoses/2 mm2 and Ki-67 index 3–20%, Grade 3 pNET a well differentiated tumor or high-grade tumor with mitotic rate > 20 mitoses/2 mm2 and Ki-67 index > 20% [6].