Pancreatic neuroendocrine tumors: current opinions on a rare, but potentially curable neoplasm

The value of MRI in identifying pancreatic neuroendocrine tumour G3 and carcinoma G3

AIM

To explore the magnetic resonance imaging (MRI) differences between pancreatic neuroendocrine tumour grade 3 (pNET-G3) and pancreatic neuroendocrine carcinoma grade 3 (pNEC-G3).

MATERIALS AND METHODS

Between 2009 and 2019, 31 patients underwent pNEN-G3 resection with preoperative MRI in two local hospitals in China. The 31 patients were assigned to a pNET-G3 group (n=13) or a pNEC-G3 group (n=18). The MRI findings between the groups were compared.

RESULTS

There was no statistically significant difference between the two groups in lesion size, clinical characteristics, or laboratory indexes. The lesions showed high or slightly higher signal on diffusion-weighted imaging and decreased apparent diffusion coefficient (ADC) values, which differed between the two groups (p=0.013). The difference between the groups regarding positive enhancement integral, arterial phase and portal phase signal enhancement ratio were statistically significant; however, the delayed phase signal enhancement ratio was not significantly different.

CONCLUSIONS

pNET-G3 and pNEC-G3 showed different characteristics on MRI. In particular, the ADC value and dynamic enhanced imaging could have an important role in distinguishing between the two.

Retinoblastoma-binding protein 2 (RBP2) is frequently expressed in neuroendocrine tumors and promotes the neoplastic phenotype

Neuroendocrine tumors (NETs), which can have survival rates as low as 4%, currently have limited therapeutic interventions available highlighting the dire need for the identification of novel biological targets for use as new potential drug targets. One such potential target is retinoblastoma-binding protein 2 (RBP2), an H3K4 demethylase whose overexpression has been linked to cancer formation and metastasis in non-endocrine tumor types. We measured RBP2 mRNA and protein levels in enteropancreatic NETs by measuring RBP2 in matched human normal and NET tissue samples. Further, proliferation, migration, invasion and colony formation assays were performed in the physiologically relevant NET cell lines βlox5, H727 and QGP-1 to understand the role of RBP2 and its demethylase activity on end points of tumorigenesis. Our data indicate a strong correlation between RBP2 mRNA and protein expression in NET specimens. RBP2 was overexpressed relative to tissue-matched normal controls in 80% of the human tumors measured. In vitro studies showed RBP2 overexpression significantly increased proliferation, migration, invasion and colony formation, whereas knockdown significantly decreases the same parameters in a demethylase-independent manner. The cell cycle inhibitors p21 and p57 decreased with RBP2 overexpression and increased upon its depletion, suggesting a regulatory role for RBP2 in cellular proliferation. Taken together, our results support the hypothesis that the aberrant overexpression of RBP2 is a frequent contributing factor to tumor formation and metastasis in enteropancreatic NETs.

Pancreatic Aetiology for Massive Upper Gastrointestinal Haemorrhage in Pregnancy

We present herein what we believe is the first reported case of massive upper gastrointestinal bleeding in pregnancy due to a pancreatic neuroendocrine tumour causing left sided portal hypertension. A 37-year-old 27-week pregnant female presented with massive haematemesis and melaena requiring transfusion of 10 units of red cell concentrate. Gastric varices were evident at endoscopy. An MRI revealed a large mass infiltrating the pancreatic tail and spleen with massive upper abdominal varix formation secondary to splenic vein invasion. A caesarean section was performed, followed by a radical en bloc partial pancreatectomy and splenectomy with resection of the fundus of the stomach and ligation of gastric and splenic varices. Her postoperative course was uncomplicated. Histology revealed a well differentiated grade 2 neuroendocrine tumour with final staging of T4N0. This case highlights an infrequently encountered cause of massive gastrointestinal bleeding. Diagnosis and management of pancreatic neuroendocrine tumours, due to their rarity and variable clinical presentation, can be challenging particularly in the setting of pregnancy where the wellbeing of a second patient must also be considered. A multidisciplinary approach with input from obstetricians and general surgeons is required when deciding optimum management, while also taking into account the patient's preferences.