Imaging Characteristics of Low-Grade Vascular Liver Tumors: HSVN and Anastomosing Hemangioma

Overview

Low-grade vascular neoplasms of the liver (LGVNL), including hepatic small vessel neoplasms (HSVN) and anastomosing hemangiomas (AH), are rare vascular tumors recently recognized and characterized histologically by small vascular channels with minimal atypia. This study describes their imaging features on dynamic CT and MRI, highlighting their differentiation from other hepatic lesions.

Background

Vascular tumors of the liver arise from endothelial cells and include common lesions such as hepatic cavernous hemangiomas, as well as more aggressive tumors like epithelioid hemangioendothelioma and angiosarcoma. LGVNL, comprising HSVN and AH, are newly identified low-grade vascular tumors with distinct histopathological features and uncertain prognosis. Imaging characteristics of LGVNL have been poorly defined, often leading to misdiagnosis and inappropriate management. This study aims to clarify the imaging appearance of these lesions to improve diagnostic accuracy.

Data Highlights

The study retrospectively analyzed 28 patients with histologically confirmed LGVNL (HSVN or AH) from two tertiary centers between 2014 and 2024. Imaging modalities included dynamic multiphase CT (23 patients), MRI (27 patients), ultrasound (19 patients), and various PET/CT scans in a subset. CT protocols included arterial, portal, and delayed phases; MRI protocols included T2-weighted, diffusion-weighted imaging, and hepatobiliary phase in 15 patients. Lesions were assessed for size, number, and enhancement patterns by experienced radiologists.

Key Findings

• LGVNL lesions are characterized histologically by small, closely packed anastomosing vascular channels with minimal cytological atypia and low proliferative index (Ki67 2–5%).
• HSVN shows infiltrative growth at the lesion periphery, whereas AH lesions are well circumscribed.
• Typical imaging features include thick peripheral lobulated arterial phase enhancement, sometimes described as a "flower petal shape."
• Lesions are often misdiagnosed as cavernous hemangiomas, metastases, or hepatocellular lesions due to overlapping imaging appearances.
• Dynamic CT and MRI protocols with multiphase contrast enhancement are essential for lesion characterization.
• Follow-up data are limited but suggest no reported recurrences or metastases, supporting a low-grade behavior.

Clinical Implications

Recognition of LGVNL imaging features can prevent misdiagnosis and inappropriate treatment. Given the infiltrative pattern of HSVN and uncertain long-term outcomes, surgical resection or close imaging follow-up is recommended. Multimodality imaging including dynamic contrast-enhanced CT and MRI is critical for accurate lesion assessment.

Conclusion

LGVNL, encompassing HSVN and AH, represent distinct low-grade vascular liver tumors with characteristic histopathology and emerging imaging features. Improved awareness and imaging characterization can guide appropriate management and follow-up strategies.

References

1. International Society for the Study of Vascular Anomalies (ISSVA) Classification
2. Recent studies on LGVNL histopathology and imaging features (2014-2024)