Hypervascular solid-appearing serous cystic neoplasms of the pancreas: Differential diagnosis with neuroendocrine tumours.

PURPOSE: To describe imaging findings of arterial hypervascular solid-appearing serous cystic neoplasms (SCNs) of the pancreas on CT and MR and determine imaging features differentiating them from neuroendocrine tumours (NETs). MATERIALS AND METHODS: We retrospectively identified 15 arterial hypervascular solid-appearing SCNs and randomly chose 30 size-matched pancreatic NETs. On CT, two radiologists in consensus assessed the size, morphology, and CT attenuation. On MR, predominant signal intensity and the amount of the cystic component on T2-weighted images and ADC maps were evaluated and compared using Fisher's exact and Student's t-test. RESULTS: The mean SCN size was 2.6 cm (range, 0.8-8.3). The CT findings were similar between the two tumours: location, shape, margin, and enhancement pattern. SCNs were significantly more hypodense on non-enhanced CT images than NETs (P = .03). They differed significantly on MR: bright signal intensity (P = .01) and more than a 10% cystic component on T2-weighted images (P = .01) were more common in SCNs than in NETs. All SCNs showed a non-restrictive pattern on the ADC map, while NETs showed diffusion restriction (P < .01). CONCLUSION: Arterial hypervascular solid-appearing SCNs and NETs share similar imaging features. Non-enhanced CT and MR images with T2-weighted images and ADC maps can facilitate the differentiation. KEY POINTS: • Frequency of hypervascular solid-appearing SCNs was 7.3% among surgically confirmed SCNs. • Hypervascular solid-appearing SCN of the pancreas can mimic pancreatic NETs. • Unenhanced CT and MR features help to differentiate the two tumours.