NET Grading WHO — SCE Medical Oncology MCQ

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EasyGI CancersNET Grading WHOSCE Medical Oncology

A 62-year-old man with a well-differentiated neuroendocrine tumour has Ki-67 measured at 18%. How is this classified in the WHO 2019 NET grading system?

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Correct answer: E — Grade 2 (G2: Ki-67 3-20%) — the WHO 2019 system grades NETs as G1 (<3%), G2 (3-20%) and G3 (>20%); G3 is further subdivided into well-differentiated NET G3 vs poorly differentiated NEC G3

WHO 2019 NET grading: G1 = Ki-67 <3% (or mitoses <2/10 HPF); G2 = Ki-67 3-20% (or mitoses 2-20/10 HPF); G3 = Ki-67 >20% (or mitoses >20/10 HPF). Crucially, G3 is subdivided: well-differentiated NET G3 (retains neuroendocrine morphology, may respond to targeted therapy/PRRT) vs poorly differentiated NEC G3 (high-grade, treated with platinum-etoposide like SCLC). This distinction has major therapeutic implications. Ki-67 and morphology together determine classification.

Reference: ESMO 2024 NET; WHO 2019 Classification; NICE