Diagnosis of Pancreatic Neuroendocrine Tumors

Abstract

Pancreatic neuroendocrine tumors (PNETs) are relatively rare; however, the incidence has increased over the last few decades. They are classified as functional or non-functional tumors according to the presence of associated clinical symptoms. The majority are non-functional tumors. For classification and staging, the World Health Organization 2010 classification system is the most commonly accepted. Chromogranin A is the most sensitive marker but has insufficient specificity. In general, PNETs are hypervascular tumors, and multiphasic contrast-enhanced computed tomography is considered the first choice for imaging study. Multiphasic magnetic resonance imaging can detect PNETs smaller than 2 cm and small liver metastasis compared with other modalities. Somatostatin receptor scintigraphy is often used in cases where functional PNETs are suspected. Positron emission tomography (PET) scan with 18F-fluorodeoxyglucose cannot visualize PNETs, but PET with 68-Ga DOTATATE can. Endoscopic ultrasonography can characterize smaller PNETs using contrast and confirm histology through fine needle aspiration or biopsy. In this article, we review the characteristics of grading systems and diagnostic modalities commonly used for PNETs.

Keywords: Computed tomography; Endoscopic ultrasonography; Magnetic resonance imaging; Pancreatic neuroendocrine tumor; World Health Organization classification.

Fig. 1.

Pancreatic neuroendocrine tumor in a 69-year-old female. A 1.0 cm size, round, hyperattenuating mass (yellow arrow) was seen in the pancreas body. The mass was not observed in non-enhanced phase (A), but highly enhanced in the early arterial phase (B). Contrast was washed out in the late arterial (C) and venous phases (D).

Fig. 2.

Pancreatic neuroendocrine tumor with cystic degeneration in a 70-year-old female. A 4.8 cm size, round, cystic mass (yellow arrow) was seen in the pancreas head. Peripheral enhancement was observed in the early arterial (A) and late arterial phases (B).

Fig. 3.

Pancreatic neuroendocrine tumor in a 59-year-old male. A 1.5 cm size, round mass (yellow arrow) was seen in the pancreas body. The mass demonstrates low signal intensity relative to the normal high signal intensity of the pancreas on T1-weighted image (A) and high signal intensity on T2-weighted image (B).

Fig. 4.

Pancreatic neuroendocrine tumor in a 47-year-old female. A 1.2 cm size, round, hyperattenuating mass (yellow arrow) was seen in the pancreas tail on computed tomography (A). The mass was well defined and displayed a hypoechoic, homogeneous pattern on endoscopic ultrasonography (B).

Fig. 5.

Pancreatic neuroendocrine tumor in a 45-year-old female. A 2.0 cm size, round, hyperattenuating mass (yellow arrow) was seen in the pancreas head on computed tomography (A). The mass was also observed on endoscopic ultrasonography with internal cystic portion (arrow head) (B).

Fig. 6.

Pancreatic neuroendocrine tumor in a 42-year-old male. A 1.5 cm size, round, hypoechoic, homogeneous mass (yellow arrow) was seen in the pancreas tail on conventional endoscopic ultrasonography (A). After contrast injection, hyperenhancement was observed in the mass on contrast-enhanced endoscopic ultrasonography (B).