MKI67 and digestive system neoplasm: Gastroenteropancreatic neuroendocrine neoplasms with proliferation index (Ki67) > 20% and/or mitoses > 20 per 2 mm2 are aggressive tumors categorized in the Grade 3 group in the WHO classification of tumors of the digestive system, with an expected 5-year survival of 16% [20–22].