Ki-67 grading of nonfunctioning pancreatic neuroendocrine tumors on histologic samples obtained by EUS-guided fine-needle tissue acquisition: A prospective study

Preoperative determination of Ki-67 expression, an important prognostic factor for grading nonfunctioning pancreatic endocrine tumors (NF-PETs), remains an important clinical challenge. To prospectively evaluate the feasibility, yield, and clinical impact of EUS-guided fine-needle tissue acquisition (EUS-FNTA) with a large-gauge needle to obtain tissue samples for histologic diagnosis and Ki-67 analysis in patients with suspected NF-PETs. Prospective cohort study. Tertiary-care academic medical center. Consecutive patients with a single pancreatic lesion suspicious for NF-PET on imaging. EUS-FNTA with a 19-gauge needle. Feasibility and yield of EUS-FNTA for diagnosis and Ki-67 expression determination. Thirty patients (mean [± SD] age 55.7 ± 14.9 years), with a mean (± SD) lesion size of 16.9 ± 6.1 mm were enrolled. EUS-FNTA was successfully performed without complications in all patients, with a mean (± SD) of 2.7 ± 0.5 passes per patient. Adequate samples for histologic examination were obtained in 28 of the 30 patients (93.3%). Ki-67 determination could be performed in 26 of these 28 patients (92.9%, 86.6% overall), 12 of whom underwent surgical resection. Preoperative and postoperative Ki-67 proliferation indexes were concordant in 10 patients (83.3%), whereas 2 patients were upstaged from G1 to G2 or downstaged from G2 to G1, respectively. Single center study with a single operator. In patients with suspected nonfunctioning low-grade to intermediate-grade pancreatic neuroendocrine tumors (p-NETs), retrieval of tissue specimens with EUS-FNTA by using a 19-gauge needle is safe, feasible, and highly accurate for both diagnosis and Ki-67 determination. A Ki-67 proliferative index acquired through this technique might be of great help for further therapeutic decisions.