The rates of tumor growth during active surveillance in a US cohort with PTCs measuring 1.5 cm or less were low. Serial measurement of tumor volumes may facilitate early identification of tumors that will continue to grow and thereby inform the timing of surveillance imaging and therapeutic interventions.

Purpose Most well-differentiated neuroendocrine tumors (WD-NETs) of the enteropancreatic system are low-intermediate grade (G1,G2). Elevated proliferation demonstrated by either a brisk mitotic rate (>20/10 high power fields) or high Ki67 index (>20%) defines a group of aggressive neoplasms designated as high grade (G3) neuroendocrine carcinoma (NEC). High grade NEC is equated with poorly-differentiated NEC (PD-NEC) and is associated with a dismal outcome. Progression of WD-NETs to a high grade neuroendocrine neoplasm very rarely occurs and their clinicopathologic and molecular features need to be characterized. Methods We investigated the 31 cases of WD-NETs with evidence of component of a high grade neoplasm. The primary sites included pancreas, small bowel, bile duct, and rectum. Histopathology of the cases was retrospectively reviewed and selected immunohistochemistry and gene mutation analyses performed. Results The high grade component occurred either within the primary tumor (48%) or at metastatic sites (52%). The clinical presentation, radiographic features, biomarkers, and the genotype of these WD-NETs with high grade component remained akin to those of G1-G2 WD-NETs. The median disease specific survival (DSS) was 55 months (16-119 months), and 2-year and 5-year DSS was 88% and 49%, respectively – significantly better than that of a comparison group of true PD-NEC (DSS 11 months). Conclusion Mixed grades can occur in WD-NETs, which are distinguished from PDNECs by their unique phenotype, proliferative indices, and the genotype. This phenomenon of mixed grade in WD-NET provides additional evidence to the growing recognition that the current WHO G3 category contains both WD-NETs as well as PDNECs.

Small bowel neuroendocrine tumors (SBNETs) have been increasing in frequency over the past decades, and are now the most common type of small bowel tumor. Consequently, general surgeons and surgical oncologists are seeing more patients with SBNETs in their practices than ever before. The management of these patients is often complex, owing to their secretion of hormones, frequent presentation with advanced disease, and difficulties with making the diagnosis of SBNETs. Despite these issues, even patients with advanced disease can have long-term survival. There are a number of scenarios which commonly arise in SBNET patients where it is difficult to determine the optimal management from the published data. To address these challenges for clinicians, a consensus conference was held assembling experts in the field to review and discuss the available literature and patterns of practice pertaining to specific management issues. This paper summarizes the important elements from these studies and the recommendations of the group for these questions regarding the management of SBNET patients.

The commonly mutated genes in pancreatic neuroendocrine tumors (PanNETs) are ATRX, DAXX, and MEN1. We genotyped 64 PanNETs and found 58% carry ATRX, DAXX, and MEN1 mutations (A-D-M mutant PanNETs) and this correlates with a worse clinical outcome than tumors carrying the wild-type alleles of all three genes (A-D-M WT PanNETs). We performed RNA sequencing and DNA-methylation analysis to reveal two distinct subgroups with one consisting entirely of A-D-M mutant PanNETs. Two genes differentiating A-D-M mutant from A-D-M WT PanNETs were high ARX and low PDX1 gene expression with PDX1 promoter hyper-methylation in the A-D-M mutant PanNETs. Moreover, A-D-M mutant PanNETs had a gene expression signature related to that of alpha-cells (FDR q-value < 0.009) of pancreatic islets including increased expression of HNF1A and its transcriptional target genes. This gene expression profile suggests that A-D-M mutant PanNETs originate from or transdifferentiate into a distinct cell type similar to alpha cells.

Objective To analyze the natural history of small asymptomatic pancreatic neuroendocrine tumors (PanNET) and to present a matched comparison between groups who underwent either initial observation or resection. Management approach for small PanNET is uncertain. Methods Incidentally discovered, sporadic, small (<3 cm), stage I–II PanNET were analyzed retrospectively between 1993 and 2013. Diagnosis was determined either by pathology or imaging characteristics. Intention-to-treat analysis was applied. Results A total of 464 patients were reviewed. Observation was recommended for 104 patients (observation group), and these patients were matched to 77 patients in the resection group based on tumor size at initial imaging. The observation group was significantly older (median 63 vs. 59 years, p = 0.04) and tended towards shorter follow-up (44 vs. 57 months, p = 0.06). Within the observation group, 26 of the 104 patients (25 %) underwent subsequent tumor resection after a median observation interval of 30 months (range 7–135). At the time of last follow-up of the observation group, the median tumor size had not changed (1.2 cm, p = 0.7), and no patient had developed evidence of metastases. Within the resection group, low-grade (G1) pathology was recorded in 72 (95 %) tumors and 5 (6 %) developed a recurrence, which occurred after a median of 5.1 (range 2.9–8.1) years. No patient in either group died from disease. Death from other causes occurred in 11 of 181 (6 %) patients. Conclusions In this study, no patient who was initially observed developed metastases or died from disease after a median follow-up of 44 months. Observation for stable, small, incidentally discovered PanNET is reasonable in selected patients.