Aggressive and Less-aggressive Cytomorphologic Variants of Neuroendocrine Tumors in Pancreas and Extra-pancreatic Abdominal Sites: A Clinicopathological Study

Summary: Introduction: Cytomorphologic variants of pancreatic neuroendocrine tumors have been recently described in the literature. Oncocytic, plasmacytoid, lipid rich and hepatoid variant are considered to be more aggressive. The study's aim was to compare the distribution of aggressive and less aggressive cytomorphologic variants of neuroendocrine tumors in pancreatic and extra-pancreatic abdominal sites (metastatic tumors). We also provide clinical follow-up in the two groups of cytomorphologic variants. Materials and Methods: A computerized search was performed to for all neuroendocrine tumors from July to April 24. We focused on neuroendocrine tumors involving pancreatic and extra-pancreatic abdominal sites (metastatic). All slides were reviewed for classification of cytomorphologic variants. Clinical charts were reviewed for available follow-up. Results: Of the 53 cases of neuroendocrine tumors (male 30 and female 23) 35 (66%) were noted in pancreatic lesions and 18 (34%) in extra-pancreatic abdominal sites [mesentery (1), lymph nodes (4), peripancreatic (2), liver (10), duodenum (1)] Distribution of aggressive and less-aggressive variants in the two groups is shown in Table 1. In Pancreatic lesions, 26% were aggressive and the remaining 74% were less-aggressive variants. In metastatic groups all cases (100%) were less aggressive variants. Average follow up was available for 44 months (range 12-120) and 41 months (range 6-96) for aggressive and less-aggressive variants, respectively. Clinical follow up of aggressive and less-aggressive variants revealed that the percentage of cases with disease, including those that died of disease (22% vs 55%, respectively) and without disease (78% versus 45%, respectively) was statistically significant (p<0.5). Conclusions: Our study shows that metastatic tumors in extra-pancreatic abdominal sites are more commonly non-aggressive cytomorphologic variants. Compared to less aggressive cytomorphologic variants, the aggressive variants had a better clinical outcome. Sample size limits our study. Further studies exploring the clinical outcome of aggressive cytomorphologic variants are required.