Background

Vascular anomalies are broadly divided into **vascular tumors** (proliferative lesions) and **vascular malformations** (structural lesions due to dysmorphogenesis). Malformations are typically **present at birth**, grow proportionally with the patient, and **do not involute** spontaneously. [@mulliken1982] [@wassef2014]

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**ISSVA**International Society for the Study of Vascular Anomalies (ISSVA) framework (clinical utility)**

The ISSVA classification organizes vascular malformations by **predominant vessel type** and **flow physiology**, which directly informs imaging strategy and treatment selection. [@wassef2014] [@issva2018] Beyond traditional imaging, indocyanine green (ICG) fluorescence imaging (ICG-FI) has emerged as a valuable tool for real-time intraoperative assessment of lesion margins and flow characteristics [@delgado-miguel2026].

| Lesion group | Typical components | Hemodynamics | Clinical implications |
| --- | --- | --- | --- |
| **Slow-flow malformations** | Capillary, **venous**, lymphatic | Low-flow / venous hypertension | Best characterized with MRI;magnetic resonance imaging (MRI); often treated with **sclerotherapy**, compression, and selective surgery. [@lee2014] [@horbach2016] |
| **Fast-flow malformations** | **AVM**,**Arteriovenous malformation (AVM)**, arteriovenous fistula | High-flow shunt with nidus (AVM) | Require **nidus-directed embolization** ± surgery; proximal occlusion alone promotes recurrence via collaterals. [@kohout1998] [@yakes1996] |
| **Combined malformations** | Mixed phenotypes (e.g., capillary–venous–lymphatic) | Variable | Frequently need staged, multimodal therapy and longitudinal care. [@wassef2014] |

**Epidemiology and burden**

- Vascular malformations are relatively common congenital lesions encountered across age groups and anatomic sites; many remain undiagnosed until growth, trauma, hormonal change, or thrombosis triggers symptoms. [@wassef2014] [@puig2003]
- AVMs can behave aggressively with progression to pain, tissue destruction, ulceration, hemorrhage, ischemia, or high-output cardiac failure in large shunts. [@kohout1998] [@puig2010]

**Clinical pearl**

- **Flow classification is the first decision point**: slow-flow lesions are generally managed with sclerotherapy-based strategies, while fast-flow AVMs require **angiographic definition and nidus eradication** strategies to reduce recurrence. [@puig2010] [@rutherford2018-rutherford]