HISTOGENESIS OF VASCULAR TUMORS IN THE PROTEUS SYNDROME

Proteus syndrome (PS) is a congenital disorder manifesting with severe deformities, the salient features being gigantism and vascular tumors . The disorder is poorly understood, and there has been much discrepan cy in the terminology regarding the vascular tumors in PS. The purpose of this study was to elucidate the histogenesis of these tumors by co rrelating microscopic observations with immunohistologic information. The value of immunoperoxidase studies in the pathologic evaluation of PS was also assessed. Fourteen formalin-fixed, paraffin-embedded tissu e specimens obtained from vascular tumors of six children with PS were stained with Ulex europaeus agglutinin I (UEA-I) lectin and the follo wing immunohistochemical reagents: anti-factor VIII-related antigen (F VIII-RAg) and anti-CD34. The tumors showed varied proportions of vascu lar, lipomatous, and fibrous tissue components consistent with vascula r hamartomas. The predominant vascular channels of the tumors were mor phologically consistent with lymphatic vessels. Immunostaining of the endothelium of these vessels was most consistently positive with UEA-I lectin. Although a color reaction product was present in small vessel s and some larger blood vessels, anti-CD34 immunostaining spared the l umens of lymphatic channels. In addition, a striking population of den dritic spindle cells was noted with the anti-CD34 but was unnoticed wi th the other reagents. We concluded that the vascular tumors of PS are primarily lymphatic hamartoma. The spindle cells noted with anti-CD34 immunostaining may relate to angiogenesis and need further delineatio n.