Pediatric Clinics of North America - CIPERJ

348 ADAMS & WENTZEL
include serious hemorrhage, thrombotic events, proteinuria, and hypertension,
mandate careful evaluation of this drug before its use in benign vascular
tumors. Another drug of potential interest is the proangiogenic agent, imiquimod.
Topical imiquimod is shown to induce regression of many tumors and to
inhibit vascular tumor growth in murine hemangioendothelioma models.
Hazen and colleagues [48] showed that the topical application of this drug
in children who have hemangiomas can cause resolution in a limited number
of patients. Imiquimod stimulates cytokines and causes breakdown and
erosion of tissue, which is one of the drug’s side effects. Becaplermin, a proangiogenic
platelet-derived growth factor gel (Regranex), has been used in
a small series of ulcerative hemangiomas, demonstrating some promising responses
[49]. Finally, drugs, such as imatinib mesilate, gefitinib, and the retinoids,
all used in childhood cancers, also could be studied for managing
vascular lesions.
Vascular malformations
Classification
Malformations are congenital abnormalities of the blood vessels and typically
are classified according to flow criteria and or the type of vessel involved
(see Fig. 1). These malformations can involve the capillaries
(capillary malformation [CM]), veins (venous malformation [VM]), arteries
(arterial malformation [AM]), or lymphatics (lymphatic malformation
[LM]). They commonly are combined lesions involving more than one blood
vessel structure (for example, capillary/venous/lymphatic malformations
[CVLM], venous/lymphatic malformations [VLM], and arterial venous malformations
[AVMs]). Vascular malformations can be associated with other
disorders or anomalies and can cause complications to vital structures and
organs.
Diagnosis
Unlike vascular tumors, vascular malformations are anomalies in the
morphologic development of the vascular system; these lesions are present
at birth and grow commensurately with the child. Vascular malformations
can be exacerbated by trauma, infection, or hormonal changes. These
lesions can result in disfigurement, skeletal abnormalities, infection, venous
stasis, and a localized consumptive coagulopathy. They can pose a surgical
risk because of hemorrhagic or thrombotic states. The role of pediatric hematologist/oncologists
again is to aid in the diagnosis and provide guidance
in the medical management.
Coagulopathy and vascular malformations
Hematologists play a key role in management of vascular malformations,
because the lesions tend to result in serious coagulopathies. Lesions at high