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 li ver of a child, review the literature, and characterize the tumor by i mmunohistochemistry and electron microscopy. We study the expression o f basic fibroblast growth factor (bFGF) and of vascular endothelial gr owth factor (VEGF) in the tumor.Materials and Methods: Clinical histor y and pathology were reviewed; sections of the tumor were studied by h istology, electron microscopy, and immunohistochemistry using antibodi es directed towards Factor-XIIla, HAM-56, bFGF and VEGF, among others. Results: The expression of VEGF resembled that of ''proliferating'' h emangiomas; however, despite being markedly elevated in the urine, bFG F could not be unequivocally detected in the tumor. A subpopulation of factor XIIIa positive cells was identified, similar to the ''intersti tial'' cells of the cellular hemangiomas of infancy. The nature and fu nction of these cells remains speculative. Conclusions: Hemangiopericy tomas are rare in the liver. When arising in this location in a child, they may clinically resemble a hemangioma, may express angiogenic fac tors in a similar fashion, and should be considered in the differentia l diagnosis.