Hemangiopericytoma of the liver: Immunohistochemical observations, expression of angiogenic factors, and review of the literature

Purpose: We describe an unusual case of a hemangiopericytoma in the liver of a child, review the literature, and characterize the tumor by immunohistochemistry and electron microscopy. We study the expression of basic fibroblast growth factor (bFGF) and of vascular endothelial growth factor (VEGF) in the tumor. Materials and Methods: Clinical history and pathology were reviewed; sections of the tumor were studied by histology, electron microscopy, and immunohistochemistry using antibodies directed towards Factor-XIIIa, HAM-56, bFGF and VEGF, among others. Results: The expression of VEGF resembled that of 'proliferating' hemangiomas; however, despite being markedly elevated in the urine, bFGF could not be unequivocally detected in the tumor. A subpopulation of factor XIIIa positive cells was identified, similar to the 'interstitial' cells of the cellular hemangiomas of infancy. The nature and function of these cells remains speculative. Conclusions: Hemangiopericytomas are rare in the liver. When arising in this location in a child, they may clinically resemble a hemangioma, may express angiogenic factors in a similar fashion, and should be considered in the differential diagnosis.