1. Imaging findings (including CT and MRI images) of both well-differentiated G3 PNET and poorly differentiated PNET were studied;
2. The CT imaging findings of G3 stage PNET and pancreatic cancer were compared to establish a Logistic regression diagnostic model, and the survival analysis of the two was compared.
3. Cox regression was used to study the risk factors for survival prognosis of well-differentiated and poorly differentiated PNET based on CT image features

According to the latest WHO Classification of Neuroendocrine Neoplasms (NET) in 2019, pancreatic neuroendocrine neoplasms (PNET) are divided into well-differentiated and poorly differentiated PNETs.The former is divided into G1, G2, and well differentiated G3.There are few studies on the survival outcomes of these two differentiated PNET types.The G3 imaging manifestations of the two types of differentiation have not been studied yet, and G3 PNET is often clinically misdiagnosed as pancreatic cancer, so it is necessary to differentiate the imaging manifestations and survival time of the two types.

A total of 71 patients with PNET in our hospital from January 2012 to January 2019 and 58 patients with pancreatic cancer from February 2014 to August 2015 were retrospectively collected. Complete survival time data of all patients after telephone follow-up were obtained.Since G3 PNET is very rare, the investigators enrolled 9 patients with G3 PNET in the First Affiliated Hospital of Zhejiang University School of Medicine and 7 patients with G3 PNET in the Affiliated Hospital of Air Force Military Medical University from January 2013 to October 2018.

CT images of PNET and pancreatic cancer were analyzed independently by two radiologists specializing in abdominal diagnosis, in which G3 lesions were evaluated simultaneously on MRI images and the others were evaluated only on CT images.Records clinical data and imaging characteristics: gender, age, tumor markers, tumor shape, size, tumor characteristics, edge, the expansion of the shrinking, pancreas, pancreatic pancreatitis, enhancement scan, arterial phase and portal phase lesions and the ratio of pancreatic parenchyma around, liver metastasis, peripheral vascular invasion, lymph node metastasis.

Inclusion Criteria:

1. Diagnosis by pathology and detailed pathological information
2. Enhanced CT examination or biopsy were performed within 2 months before surgery
3. There was no preoperative radiotherapy or chemotherapy

Exclusion Criteria:

1. No Ki-67 index
2. CT value cannot be measured by ROI because of pancreatic atrophy and other reasons
3. No enhanced images or missing images

The investigators retrospectively analyzed data for patients who underwent contrast-enhanced MDCT for the evaluation of G3 PNETs at the Second Affiliated Hospital of Zhejiang University School of Medicine (n = 12) between January 2011 and May 2019, patients with G3 PNET who underwent MDCT at the First Affiliated Hospital of Zhejiang University School of Medicine (n = 4) and the Military Medical University of Air Force (The Fourth Military Medical University) (n = 4) between January 2013 and October 2018, and consecutive patients with PDAC who underwent MDCT at the Second Affiliated Hospital of Zhejiang University School of Medicine (n = 58) from February 2014 to August 2015.