Classification and Grading of Neuroendocrine Tumors

Jonathan R. Strosberg, MD, of Moffitt Cancer Center, walks through the classification of neuroendocrine neoplasms with Simron Singh, MD, MPH, of Sunnybrook Odette Cancer Centre, and moderator Daniel M. Halperin, MD, of Winship Cancer Institute of Emory University. Strosberg explains that the first distinction, well differentiated vs poorly differentiated, rests on morphology, and that poorly differentiated neuroendocrine carcinomas are always high grade, usually with a Ki-67 above 50%. Well-differentiated neuroendocrine tumors (NETs) are graded by proliferative index: grade 1 below 3%, grade 2 from 3% to 20%, and grade 3 above 20%. A proposed system would replace typical and atypical carcinoid terminology for lung NETs with grades 1 through 3. Singh cautions that grade is one prediction from a single sample at one point in time, and that somatostatin receptor status, dual positron emission tomography (PET) imaging, genomic clustering, growth rate, and symptom burden now fit together like a Rubik's cube.