Etiology
The etiology of hemangioma is poorly understood. Both intrinsic and extrinsic mechanisms have been proposed. There is much debate regarding the origin of the precursor cell to hemangioma.
Pathophysiology
Infantile hemangioma may originate from the embryonic mesoderm, a pericyte or endothelial precursor, or localized angioblasts.
According to the intrinsic theory, infantile hemangioma originates from vasculogenesis, a process by which new blood vessels are formed.
Extrinsic theory suggests that external environmental factors provide an environment favorable for the development of infantile hemangioma. Proposed stimulants include hypoxia, local growth factors, cytokines, and estrogens. Hemangioma could develop as a result of vasculogenesis or angiogenesis, whereby new blood vessels arise from existing ones.
Within both intrinsic and extrinsic theories, the precursor cell of the infantile hemangioma originates from the embryo.[14][20] Several characteristic cellular placental markers have been identified in infantile hemangioma. Debate exists as to whether the precursor cell may be a displaced placental angioblast; however, molecular genetic studies of infantile hemangioma point toward an embryonic origin for the precursor cell. Hemangioma endothelial cells (HECs) from male infants contain XY chromosomes. Genetic polymorphisms of the HECs match those of the child, not the mother. Thus, if the precursor cell arises from the embryo, it may develop toward a placental phenotype.[21][22]
Classification
Infantile hemangiomas are classified as vascular tumors in the International Society for the Study of Vascular Anomalies classification, which was last updated in April 2014.
International Society for the Study of Vascular Anomalies: classification for vascular anomalies
Opens in new window Tumors in this classification structure share the characteristics of growth and endothelial proliferation.[Figure caption and citation for the preceding image starts]: Examples of infantile hemangiomas according to International Society for the Study of Vascular Anomalies classificationInternational Society for the Study of Vascular Anomalies; used with permission [Citation ends].
Clinical classification[4][5]
Superficial
Most common type of hemangioma, comprising 43% of total; located in the superficial dermis and characterized by bright-red color in the growth phase.
Deep
16% of total, located in the deep dermis and subcutaneous tissues; may present later in life as blue nodule.
Mixed (superficial and deep)
41% of total; appear as combination of deep blue nodules with overlying bright red superficial plaque.
Morphologic classification[6][7]
Localized
Arises from a single focus; often round or oval in shape.
Segmental
Seem to arise from a broad area; can be associated with underlying abnormalities such as those seen in PHACES syndrome (posterior fossa malformations, hemangioma, arterial anomalies, coarctation of the aorta and cardiac defects, eye abnormalities, and sternoclavicular or supraumbilical anomalies) or LUMBAR syndrome (lower body infantile hemangioma and other cutaneous defects, urogenital anomalies and ulceration, myelopathy, bony deformities, anorectal malformations and arterial anomalies, and renal anomalies).[1]
Indeterminate
Ambiguity in characteristics that defies classification as focal or segmental.
Clinical variants and special considerations
Segmental hemangiomas may have associated underlying abnormalities. Segmental cervicofacial hemangiomas may have associated structural anomalies of the brain, cerebral vasculature, eyes, sternum, and/or aorta. This neurocutaneous disorder is known as PHACE(S) syndrome, with the acronym referring to posterior fossa anomalies, hemangioma, arterial lesions, cardiac abnormalities/aortic coarctation, abnormalities of the eye, and sternal clefting or supraumbilical raphe.[8] Infants with segmental cervicofacial hemangioma require ophthalmologic examination, echocardiogram, and possible central nervous system imaging.
Beard hemangioma: hemangiomas located on the lower face and neck have been associated with laryngeal hemangioma.[1] Progressive stridor is a worrisome sign. Infants with hemangiomas in beard distribution should be referred to an otolaryngologist for further evaluation and possible endoscopy.[1]
Lumbosacral hemangioma: hemangioma located in the lumbosacral area may signal underlying spinal dysraphism. Other associated malformations include tethered cord, renal, and skeletal anomalies. Magnetic resonance imaging is the test of choice.[1][9][10] Segmental perineal hemangiomas should raise concern for LUMBAR syndrome, which refers to lower body infantile hemangioma and other cutaneous defects, urogenital anomalies and ulceration, myelopathy, bony deformities, anorectal malformations and arterial anomalies, and renal anomalies.[1]
Multifocal infantile hemangiomas (previously termed diffuse neonatal hemangiomatosis): Infants with multiple cutaneous hemangiomas may have hemangiomas within their visceral organs.[11] A prospective study revealed that 16% of infants who present with ≥5 infantile hemangiomas have hepatic hemangiomas.[12] In such patients a good physical exam is indicated. Hepatomegaly may indicate clinically significant liver hemangiomas and should be evaluated by ultrasound. An abnormal cardiac exam may indicate high-output heart failure.
Hemangiomas in certain locations can result in significant cosmetic or functional complications. Periorbital hemangiomas may result in ocular complications. Hemangiomas on the nasal tip or ear may cause cartilage destruction and permanent disfigurement. Lip hemangiomas can distort the normal contour of the mouth.[13] Genital and perineal hemangiomas are more likely to ulcerate and lead to associated complications. [Figure caption and citation for the preceding image starts]: Plaque-type cervicofacial ulcerated hemangioma (beard distribution)From the collection of Carla T. Lane, MD, PhD; used with permission [Citation ends].
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