Hepatic small vessel neoplasms (HSVN) are low-grade vascular lesions of uncertain malignant potential.
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Terminology
Although also referred to as hepatic small vessel hemangiomas 3, this term may wrongly mislead HSVN to represent a subtype of hepatic hemangiomas and, therefore, will be avoided in this article.
Epidemiology
First described in 2016 2, at the moment there are 22 cases reported in the literature 1. Considering this and having some imaging features that could resemble hemangiomas, it is possible that HSVNs are underdiagnosed.
Clinical presentation
No particular clinical presentation has been associated with HSVMs so far, with most reported cases identified incidentally 1. Larger lesions are associated with epigastric fullness or right upper quadrant discomfort 2,4.
Pathology
HSVNs are true vascular neoplasms with an infiltrative growth and are characterized by thin-walled vascular spaces lined by flat to plump-ovoid endothelial cells but minimal cytologic atypia and mitotic activity 1-3. The main histological differential diagnosis is made with well-differentiated angiosarcoma 4,5.
Radiographic features
Focal well-defined liver lesions of variable size; multiplicity has been described.
CT
On non-contrast scans, the lesions are usually hypoattenuating masses.
Multiphase post-contrast images demonstrate a thick continuous peripheral enhancement with central areas of nonenhancement. The contrast avidity has been reporting as marked and superior to the aortic blood pool on both portal and delayed phases 3,5. Centripetal enhancement with either complete central enhancement or washout on delayed phase have been described 5.
MRI
- T1: sharply marginated, hypointense mass
- T1 C+ (Gd): thick continuous and early peripheral enhancement
- T2: markedly T2 hyperintense 5
- DWI/ADC: no diffusion restriction 5
Treatment and prognosis
Although described as a low-grade neoplasm, the long-term malignant potential of HSVNs remain uncertain and imaging follow-up has been advised 4.
Differential diagnosis
- hepatic hemangioma: peripheral globular discontinuous enhancement
- hepatic angiosarcoma
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