Congenital Vascular Anomalies: Classification and Terminology

Infantile Hemangiomas

Infantile hemangiomas (IHs) make up 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. Head and neck regions are involved most frequently (60% of cases), followed by the trunk (25% of cases) and extremities (15% of cases).

IHs have a characteristic life cycle where they are typically not present at birth but appear commonly within the first 6 weeks of life as a soft, noncompressible mass that grows rapidly in the first few months (proliferative phase) and gradually involutes over years (involutional phase) and remains as a variable amount of smaller fibrofatty tissue for the remainder of life. IHs typically manifest as a single superficial cherry-red “strawberry mark”; deeper IHs are firm, rubbery subcutaneous masses, sometimes with a bluish skin hue. Most IHs double in size in the first 2 months of life, and approximately 80% reach their maximum size by 6 months of age ( Fig. 16.1 ).

Spontaneous regression in early childhood (approximately 7 years of age) is typical, but up to 40% of IHs may have residual skin changes, especially if they involve the head and neck. When a single lesion has a typical clinical history in a territory with no concern, no imaging or intervention is required. However, there are several situations in which further evaluation and treatment may be required. An atypical history requires US evaluation, which typically demonstrates a heterogenous mass with high vascularity on duplex scanning with low resistive arterial waveforms that become increasingly resistant during involution. If five or more subcutaneous lesions are present, then US of the liver is required. MRI reveals a T2 bright, T1 isointense mass with homogenous avid contrast enhancement. Internal serpiginous flow voids within the IH noted in T2-weighted imaging represents the arterial inflow, an important diagnostic clue. Dynamic contrast-enhanced 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.

Complications of IH include hypothyroidism, heart failure, abdominal compartment syndrome, visual impairment (periorbital), ulceration, and bleeding.

There is an association with more widespread abnormalities. PHACES syndrome refers to a constellation of Posterior fossa brain malformations, Hemangiomas, Arterial anomalies, Coarctation of the aorta and cardiac defects, Eye abnormalities, and Sternal defects.

Patients with hemangiomas overlying the lumbosacral spine can have associated abnormalities, the most common of which is a tethered spinal cord. MRI should be performed to exclude this abnormality. Genitourinary anomalies are possible, although less common.

Airway hemangiomas should be investigated in patients who have cutaneous cervicofacial hemangiomas distributed in the chin, anterior neck, lower lip, and preauricular areas (a “beard” distribution).

Therapy is reserved for those infants in whom there are complications or impingement on vital structures; oral propranolol has largely replaced oral steroids as the therapy of choice, although topical timolol is frequently used for isolated cutaneous lesions. Surgery may be required in some situations. The immunohistochemical marker glucose transporter protein isoform 1 (GLUT1) has become a major tool in diagnosing infantile hemangioma, with endothelial cells staining strongly. Most other vascular lesions, including congenital hemangiomas and vascular tumors, do not stain positive for GLUT1 ( Fig. 16.2 ).

Congenital Hemangiomas

Congenital hemangiomas (CHs) can occur as soft tissue masses, visceral lesions, and intracranial extraaxial lesions. There are three distinct life cycles: RICH ( Fig. 16.3 ), NICH ( Figs. 16.1 and 16.4 ), and PICH. The proliferative phase is complete by birth, although acute enlargement can be secondary to intralesional hemorrhage. They often present 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 RICHs, 90% of involution has occurred at 3 months, with complete resolution by 14 months. NICHs may occasionally grow commensurate with infant growth. Clinically lesions may be associated with a mild consumptive coagulopathy. Imaging is generally not required in CH, but MRI typically demonstrates rim enhancement, which becomes confluent throughout the lesion in time. Histology demonstrates the endothelial cells lining the CH stain negative to GLUT1. Presently no medical therapy has been shown to confer benefit. Surgery is rarely required; however, RICHs can leave significant textural change, necessitating reconstructive surgery after involution.

Tufted Angiomas

Tufted angiomas (TAs) are also known as progressive capillary hemangiomas or angioblastoma of Nakagawa and are cutaneous lesions. TA is associated with Kasabach-Merritt phenomenon, a profound and sustained coagulopathy in which platelets, fibrinogen, and red blood cells are trapped within the lesion. There is speculation that TAs and KHEs are a spectrum of the same entity, with KHE being more aggressive. Histologically TAs contain distinct “cannonball” clusters of packed capillaries and the endothelial cells stain positive for lymphatic marker PROX1.

Pyogenic Granuloma

Pyogenic granuloma (PG), also known as lobular capillary hemangioma, is typically identified in the face, nose, or neck regions as a focal, well-defined superficial lesion of <1 cm. These lesions are extremely vascular and have a tendency to bleed and ulcerate and are associated with a history of recent trauma or inflammation.

Kaposiform Hemangioendothelioma

KHE is a rare, distinct vascular tumor. 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. The destructive/infiltrative nature and rapid growth of this vascular tumor facilitates differentiation from IH. Kasabach-Merritt phenomenon, a profound and sustained coagulopathy that can be life threatening, can be seen in up to 70% of patients. KHE has a high mortality rate (30%) related to coagulopathy or complications from local tumor infiltration.

KHE can occur anywhere but has a preponderance for extremities and the retroperitoneum. The lesions are firm and indurated and have a purplish coloration in which regional nodal spread has been described without true metastases ( Figs. 16.1 and 16.5 ). KHE appears as a solid mass with ill-defined borders and variable echogenicity on US imaging. MRI demonstrates an infiltrative pattern, with crossing of multiple soft tissue planes and involvement of overlying skin and subcutaneous fat often associated with surrounding edema. Diffuse early enhancement is typical. These more aggressive imaging features distinguish KHE from IH, as do the atypical clinical features.

Histologically KHE consists of coalescing lobules of spindle cells that stain positive for PROX1 (lymphatic marker), CD34 (a stem cell marker), and CD31 (a vascular endothelial marker).