I. INTRODUCTION. Vascular anomalies affect approximately 5% of the population and can involve any component of the vasculature. The field is confusing because different lesions may look similar and terminology is difficult. Vascular anomalies are classified based on their clinical behavior and cellular characteristics (Table 66.1). The International Society for the Study of Vascular Anomalies (ISSVA) has recently released an expanded classification. Ninety percent of lesions can be diagnosed by history and physical examination. There are two broad types of vascular anomalies: tumors and malformations. Tumors typically arise postnatally and demonstrate endothelial proliferation. There are four major lesions: (i) infantile hemangioma, (ii) congenital hemangioma, (iii) kaposiform hemangioendothelioma, and (iv) pyogenic granuloma (Fig. 66.1). Vascular malformations are errors in vascular development, are present at birth, and have minimal endothelial turnover. There are four major categories: (i) capillary malformation, (ii) lymphatic malformation, (iii) venous malformation, and (iv) arteriovenous malformation (Fig. 66.2).

A. Infantile hemangioma. Infantile hemangioma (IH) is the most common tumor of infancy, affecting 4% to 5% of infants. IH is more frequent in premature children and in females. The median age of appearance is 2 weeks. IH is red when it involves the superficial dermis and can appear bluish if it is located beneath the skin. IH grows faster than the child during the first 9 months of age (proliferating phase); 80% of its size is achieved by 3.2 (±1.7) months. The majority of IH are small, harmless lesions that can be monitored under the watchful eye of a pediatrician. However, a minority of proliferating IH can cause significant deformity or complications. Infants with five or more small (<5 mm) tumors are more likely to have IH of the liver, although the risk is low (˜16%). After 12 months, the tumor begins

to regress (involuting phase). Involution ceases in most of children by age 4 years (involuted phase). After involution, one-half of children will have a residual deformity.

Most IHs are simply observed. To protect against ulceration, IH should be kept moist with hydrated petroleum during the proliferative phase. If ulceration develops, the wound is washed gently with soap and water at least twice daily. Small, superficial areas are managed by the application of topical antibiotic ointment and occasionally with a petroleum gauze barrier. Large, deep ulcers require damp-to-dry dressing changes. Bleeding from an ulcerated IH is usually minor and is treated by applying direct pressure. Ulcerations will heal with local wound care within 2 to 3 weeks.

A diffuse hemangioma replacing hepatic parenchyma necessitates thyroid-stimulating hormone (TSH) monitoring to prevent potentially devastating and irreversible effects on neurologic function. Hypothyroidism results from the expression of a deiodinase by the hemangioma which cleaves iodine from thyroid hormone and inactivates it. Massive intravenous thyroid replacement may be necessary until the hemangioma regresses. In contrast to diffuse hepatic hemangioma, a large single hemangioma in the liver is often a rapidly involuting congenital hemangioma and does not
require intervention. Similarly, multiple small hepatic hemangioma do not cause morbidity unless significant shunting is present.