Ki-67 and presence of liver metastases identify different progression-risk classes in pancreatic neuroendocrine neoplasms (pNEN) undergoing resection.

In pancreatic neuroendocrine neoplasms (pNEN), size ≤2 cm and Ki-67 < 3% suggest indolent behavior, but no factor alone predicts prognosis. We investigated factors predictive of tumor progression in 80 pNENs surgically resected in a single Institution from 1995 to 2015. At multivariable analysis the only two independent variables related to PFS were Ki-67 (HR 2.97; 95%CI 1.26–7.02) and presence of synchronous liver metastases (HR 3.60; 95%CI 1.70–7.61). Using Ki-67 < 3% and M0 as reference, the HR for tumor progression was 3.21 (95%CI 1.18–8.74) for M0 patients with Ki-67 3–20%, 5.06 (2.29–11.2) for M1 patients with Ki-67 ≤ 20% and 24.3 (6.64–89.2) for those with Ki-67 > 20%. Tumor size (≤2 vs. >2 cm) was not a predictive factor at any analysis. Intra-class correlation of Ki-67 values on pre-surgical biopsies vs. surgical specimens was 0.99 and Ki-67 classes were correctly identified in 97% of biopsies.