Background: Infantile hemangiomas are common tumors, distinctive for their perinatal presentation, rapid growth during the first year of life, and subsequent involution-and for their expression of a unique immunophenotype shared by placental microvessels. Occasional "hemangiomas" differ from the classic form in presenting fully formed at birth, then following a static or rapidly involuting course. These congenitally fully developed lesions have generally been assumed to be clinical variants of more typical, postnatally developing hemangiomas. This assumption has not been tested by rigorous histologic and immunophenotypic comparisons.
Objective: To compare the histologic and immunohistochemical features of congenital nonprogressive hemangiomas with those of typical, postnatally proliferating, hemangiomas.
Design: All cellular vascular tumors resected from infants younger than 4 months at Arkansas Children's Hospital, Little Rock, over the past 20 years (43 lesions from 36 patients) were first characterized histologically and immunohistochemically, then clinically by chart review.
Setting: A university-affiliated pediatric hospital.
Main outcome measures: Histologic appearance, immunoreactivity for the infantile hemangioma-associated antigens GLUT1 and LeY, and clinical behavior.
Results: Congenital nonprogressive hemangiomas differed from postnatally proliferating infantile hemangiomas in histologic appearance and immunohistochemical profile. Distinguishing pathologic features of these tumors were lobules of capillaries set within densely fibrotic stroma containing hemosiderin deposits; focal lobular thrombosis and sclerosis; frequent association with multiple thin-walled vessels; absence of "intermingling" of the neovasculature with normal tissue elements; and lack of immunoreactivity for GLUT1 and LeY.
Conclusion: Congenital nonprogressive hemangiomas are histologically and immunophenotypically distinct from classically presenting hemangiomas of infancy, unlikely to be related to the latter in pathogenesis.