Table 1

Classification of neuroendocrine neoplasms according to pathological differentiation and grade according to Ki-67 proliferation index

DifferentiationKi-67 (%)GradeClassification of neuroendocrine neoplasm (NEN)
Well differentiated<31 (G1)NET
Well differentiated3–202 (G2)NET
Well differentiated>20, usually <55%3 (G3)NET
Poorly differentiatedUsually >55%3 (G3)NEC
  • NEC, neuroendocrine carcinoma; NET, neuroendocrine tumour.