Congenital Vascular Anomalies

Classification and Terminology

Aylin Tekes, Özlem Tuğçe Kalayci and Sally E. Mitchell

Biological Classification of Congenital Soft-Tissue Vascular Anomalies

The classification of vascular anomalies is confusing to most physicians. Overlapping clinical and imaging findings, the rarity of the vascular anomalies, lack of physician experience with the entity, and lack of a multidisciplinary approach in many centers contribute to the chaos in diagnosis and management of vascular anomalies.

To clarify this situation, the correct terminology for each entity should be consistently used. Even as recently as 2009, Hassanein and Mulliken found that the term hemangioma was used incorrectly in 71.3% of publications that year.¹ This emphasizes the importance of understanding the current classification system that was approved by the International Society for the Study of Vascular Anomalies (ISSVA) in 1996 (Table 43-1), which stems from the biological behavior–based classification system introduced by Drs. Mulliken and Glowacki in 1982.²

Congenital soft-tissue vascular anomalies can present anywhere in the body from head to toe, with variable size and infiltration, so a multidisciplinary approach is crucial in the management/treatment of these patients. Consistent use of correct terminology will improve communication between different specialists and avoid misunderstandings.

Given the rarity of some of the vascular anomalies, as well as overlapping clinical and imaging features, the experience of the team taking care of the patient is extremely important. Accurate classification and treatment of vascular anomalies is best performed by groups who see a large volume of patients and can begin to see the patterns of vascular anomalies in coordinated clinical and imaging appearances. This is why development of multidisciplinary vascular anomalies centers is essential for accurate diagnosis and management of these patients. In our clinical practice, we often see patients who say that their doctor had never seen anything like that before and had no idea what it was, let alone how to treat it.

Vascular anomalies can be imaged by ultrasonography (US), computed tomography (CT), computed tomographic angiography (CTA), digital subtraction angiography (DSA), magnetic resonance imaging (MRI), and MR angiography/venography (MRA/MRV). US is often used as first-line imaging, given its lack of ionizing radiation, no need for sedation/general anesthesia, and bedside imaging capabilities. Structural imaging data can be combined with flow dynamics of the vascular anomaly, which is very valuable for classification. However, operator dependence and small field of view are limiting factors in diagnosis and follow-up. MRI sets the gold standard in most cases, given its high soft-tissue resolution, different sequences, and fat-suppression capabilities, enabling clear differentiation/demarcation of the vascular anomaly from surrounding soft tissues, along with dynamic contrast-enhanced (CE) imaging information. The full anatomic extent of the anomaly can be evaluated in relation to adjacent nerves, and MRA/MRV can identify the feeding artery and draining vein. Response to treatment can be reliably evaluated over time by changes in size and flow characteristics.

In this chapter, we will review the ISSVA classification system, which will include both common vascular anomalies and the more complex syndromes. We will describe the clinical presentation and imaging findings of each group/subgroup of vascular anomalies, using a practical approach to correlate clinical presentation with imaging findings (Fig. 43-1 and Table 43-2).

TABLE 43-2

Key Magnetic Resonance Imaging Features of Vascular Anomalies

	IH	VM	LM	AVM
Solid mass	Yes	No	No	No
Phlebolith	No	Yes	No	No
Enhancement	Avid homogenous	Variable	None (cysts’ periphery)	Avid serpiginous
DCE-MRA	Arterial	Venous	None	Arterial with early venous drainage

AVM, Arteriovenous malformation; DCE-MRA, dynamic contrast-enhanced magnetic resonance angiography; IH, infantile hemangioma; LM, lymphatic malformation; VM, venous malformation.

Vascular anomalies are divided into two main groups: vascular tumors and vascular malformations.³ The morbidity and treatment for vascular tumors differ dramatically from vascular malformations, and also differ dramatically for each type of vascular tumor and each type of vascular malformation, which is the overriding impetus for clear, standardized classification in the first place.

Vascular Tumors

Vascular tumors include infantile hemangiomas (IHs); congenital hemangiomas, including noninvoluting congenital hemangiomas (NICHs) and rapidly involuting congenital hemangiomas (RICHs); and kaposiform hemangioendotheliomas (KHEs). Age at presentation (prenatal, at birth, early childhood/adult), presence or absence of overlying telangiectatic vessels, a lighter peripheral ring, presence of fast-flow, and temporal evolution of the mass (involution vs. no involution) are important clinical criteria to approach the diagnosis of vascular tumors.

Infantile Hemangiomas

IHs comprise approximately 90% of all vascular tumors. They are the most common vascular tumors of infancy, with a higher incidence in white infants. The highest incidence is noted in preterm infants weighing less than 1000 g.⁴ Head and neck regions are involved most frequently (60% of cases), followed by the trunk (25% of cases), and extremities (15% of cases).⁵

IHs are often not apparent at birth but most appear within the first 6 weeks of life as a soft, noncompressible mass with a typical triphasic evolution: proliferation, plateau, and involution. Superficial hemangiomas are generally cherry red macules and papules; deep hemangiomas are firm, rubbery subcutaneous masses, sometimes with a bluish skin hue. Compound hemangiomas combine aspects of both types. Most IHs double in size in the first 2 months of life, and approximately 80% reach their maximum size by 6 months of age.⁶

Spontaneous regression in early childhood (≈7 years of age) is typical,7,8 but up to 40% of IHs may have residual skin changes and fibrofatty residuum, especially if they involve the head and neck. Patients with large IHs in the head and neck region—where there may be a concern for airway compromise, ulceration, or bleeding—can be medically treated, and propranolol is the leading drug of choice (Fig. 43-2; also see Fig 43-1).

FIGURE 43-2 A, This 10-week-old infant girl had multiple segmental facial red hemangiomas, ulceration on bottom lip, and subcutaneous hemangioma of left upper medial eyelid that caused swelling and partial obscuring of left eye. B, Same patient after 9 months on propranolol. Note degree of involution of lesions shown in A. C, Magnetic resonance imaging of 6-month-old girl with palpable soft mass in left lateral neck, an infantile hemangioma (IH). Axial T2-weighted image with fat saturation demonstrates well-defined hyperintense soft-tissue mass in left neck, with few internal serpiginous flow voids. D, Same patient as in C; postcontrast T1-weighted image with fat saturation demonstrates avid homogenous internal contrast enhancement of the solid vascular mass. E, Same patient as in C; time-resolved dynamic contrast-enhanced magnetic resonance angiography (DCE-MRA) in arterial phase demonstrates that avid homogenous enhancement of IH starts in arterial phase (note that only arteries are enhanced, no veins visualized) from a feeding artery taking off from left external carotid artery. Serpiginous flow voids noted in C were demonstrated to represent feeding arteries and draining veins of the IH. Note draining vein into left subclavian/internal jugular junction **(F).**

The immunohistochemical marker glucose transporter protein isoform 1 (GLUT1) has become a major tool in diagnosing infantile hemangioma, with endothelial cells staining strongly.²¹ The overwhelming majority of other vascular lesions, including congenital hemangiomas and vascular tumors, do not stain positive for GLUT1.^9,10

Imaging is not required for the majority of IHs but can be useful to confirm the suspected diagnosis in atypical lesions, to determine the extent of deep lesions, and to exclude other vascular tumors (such as KHE) or soft-tissue malignancies. US demonstrates a solid mass with increased color flow within the mass.¹¹ The arterial inflow and venous drainage can be visualized by Doppler US.¹²

MRI reveals a T2 bright, T1 isointense mass with homogenous avid contrast enhancement.¹³ Internal serpiginous flow voids within the IH noted in T2-weighted imaging represents the arterial inflow, an important diagnostic clue. Dynamic contrast-enhanced MRA (DCE-MRA) demonstrates early arterial enhancement in a soft-tissue mass with a draining vein. Typically, no perilesional edema is observed, which facilitates differentiation from other soft-tissue malignancies. Fibrofatty infiltration can be observed during the involuting phase.

Congenital Hemangiomas

Unlike IH, congenital hemangiomas are fully formed at birth, with nearly no growth after birth, and lack positive staining with GLUT1.

Clinically, RICH (Fig. 43-3) and NICH (Fig. 43-4; also see Fig. 43-1) appear similar, often presenting as violaceous gray tumors with prominent overlying veins or telangiectases that extend beyond the periphery of the lesion. Many have a lighter or bluish halo on the surrounding skin. In practice, RICH and NICH are distinguished in retrospect, since the former involutes by 12 months of age, and the latter involutes either partially or not at all and requires surgical excision. In addition, RICH can leave significant textural change necessitating reconstructive surgery after involution.¹⁴

FIGURE 43-3 A, Newborn with round purple mass on right thigh. Note coarse telangiectasia of skin and peripheral pallor typical of congenital hemangiomas. B, Same patient at 5 months of age. Note that lesion has spontaneously involuted very rapidly, confirming this is a rapidly involuting congenital hemangioma (RICH).

Early and accurate diagnosis is critical to avoid unnecessary biopsy/surgical intervention.¹⁵ Similar histologic and clinical features of RICH and NICH raise the possibility that the latter may undergo involutional arrest to become a noninvoluting tumor.¹⁶

Kaposiform Hemangioendothelioma

KHE is a rare, distinct vascular tumor.¹⁷ It may present at birth or within the first few months of life as an ill-defined purpuric mass, often painful, with an encircling pale ring; however, presentation may be later in childhood.¹⁸ The destructive/infiltrative nature and very rapid growth of this vascular tumor facilitates differentiation from IH. Kasabach-Merritt phenomenon (KMP, a rare life-threatening condition in which a vascular tumor traps and destroys platelets) can be seen up to 50% of patients. KHE has a high mortality rate (24%) related to coagulopathy or complications from local tumor infiltration.

The firm, indurated lesion of KHE has a more invasive appearance and a purplish coloration (Fig. 43-5; also see Fig. 43-1). These cells form slitlike lumina containing erythrocytes that resemble Kaposi sarcoma, thus the name kaposiform hemangioendothelioma

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