The following guidelines provided by the World Health Organization (WHO) [1] and the European Neuroendocrine Tumor Society [5] outline the criteria for tumor grading based on Ki-67 LI: (1) grade 1, Ki-67 LI < 2%; (2) grade 2, Ki-67 LI between 3 and 20%; and (3) grade 3, Ki-67 > 20%. The gene discussed is MKI67; the disease is neoplasm.