Prediction of lymph node metastasis in pancreatic neuroendocrine tumors by contrast enhancement characteristics

Background Iso- or hypo-attenuating areas in the arterial phase on contrast-enhanced computed tomography (CE-CT) have been reported to be negative prognostic features in pancreatic neuroendocrine tumors (PNETs). Given that the optimal indication for lymph node dissection in patients with PNET remains unclear, we sought to utilize enhancement characteristics on CE-CT as a preoperative predictor of regional lymph node metastasis in PNETs. Methods The medical records of patients with well-differentiated PNETs who underwent pancreatectomy along with lymphadenectomy were retrospectively analyzed. We divided PNETs into two groups based on the extent of attenuation in the late arterial phase on CE-CT imaging. PNETs that showed hyper-attenuation over the entire area compared to the adjacent normal pancreas were categorized as hyper-PNETs. PNETs that contained both hyper and iso- or hypo-attenuation regions as well as those that showed only iso- or hypo-attenuation over the entire area were categorized as hetero/hypo-PNETs. Results Forty-one patients with a median age of 64 years were enrolled, including 11 with hyper-PNETs and 30 with hetero/hypo-PNETs. Hetero/hypo-PNETs were significantly larger than hyper-PNETs (P = 0.022), and the former group more frequently comprised G2 tumors, according to the World Health Organization 2010 classification (P < 0.001). On univariate and multivariate analyses, hetero/hypo-PNETs were independently associated with regional lymph node metastasis. Conclusions The presence of iso- or hypo-attenuating regions appears to be associated with regional lymph node metastasis in PNETs. Tumor enhancement characteristics should be assessed in patients with PNET so as not to miss those at high risk of lymph node metastasis.