Imaging features of recently identified low-grade vascular neoplasia of the liver: hepatic small vessel neoplasm and anastomosing hemangioma.

Objectives: The aim of this study was to describe the imaging features on dynamic CT and MRI of a series of pathologically confirmed low-grade vascular neoplasia of the liver (LGVNL).

Materials And Methods: In this retrospective multicenter study, patients diagnosed with pathologically proven LGVNL between January 2014 and August 2024 and with cross-sectional imaging (CT or MRI) were included. Based on prior studies, we divided the patients into two groups: a group with typical LGVNL features and a group with atypical tumors. Univariable analysis and the logistic regression model were used to evaluate the outcome of typical and atypical LGVNL features.

Results: Twenty-eight patients were included (20 men, mean age 53.7 ± 13.4 [SD] years old). The median size of tumors at diagnosis was 22 mm [IQR, 10-80]. A typical LGVNL pattern including thick continuous peripheral arterial phase "flower petal shape" enhancement was found on MRI in 67% (18/27) with lobulated lesions (p = 0.001), a marked hypersignal on T2-weighted images (p = 0.003) and a high apparent diffusion coefficient (ADC) (mean tumor ADC, 2.1 × 10 ± 0.3 [SD] mm/s) (p = 0.006) with portal and delayed phase filling following contrast administration. An atypical LGVNL pattern was found in 33% (9/27), including homogeneous arterial phase enhancement that persisted during the portal and delayed phases. After a median follow-up of 16 months, tumor growth was observed in 42% (8/19) and was faster in patients with the atypical LGVNL pattern (p = 0.013).

Conclusion: The typical imaging pattern of LGVNL that includes arterial phase "flower petal shape" enhancement with a marked hypersignal on T2-weighted images and a high ADC was seen in most cases.

Key Points: Question Low-grade vascular neoplasia of the liver, including hepatic small vessel neoplasms and anastomosing hemangioma, is a new entity of vascular tumors with few radiological descriptions. Findings Diagnostic imaging criteria include the "flower petal shape" enhancement pattern on arterial phase, a marked hypersignal on T2-weighted images and high ADC values. Clinical relevance This multicenter study provides clinical, pathological and imaging data on low-grade vascular neoplasia of the liver and highlights specific imaging features for its diagnosis. Knowledge of these imaging features helps eliminate differential diagnoses.