DIFFUSE SINUSOIDAL HEMANGIOMATOSIS OF THE SPLEEN - A CASE-REPORT WITHENZYME-HISTOCHEMICAL, IMMUNOHISTOCHEMICAL, AND ELECTRON-MICROSCOPIC FINDINGS

Diffuse hemangiomatosis of the spleen is a very rare benign tumor in w hich the whole spleen is permeated by neoplastic blood vessels. It is occasionally accompanied by severe disturbances of blood coagulation. The histogenesis of this tumor remains obscure. No systematic investig ations of the immunophenotype of the neoplastic endothelium have been published. We describe a case of isolated benign diffuse hemangiomatos is of the spleen in which the enzyme-histochemical and immunohistochem ical findings suggested an origin in the splenic sinus endothelial cel ls. Some of the tumor endothelial cells reacted with UEA-1, BMA 120, a ntibodies against the von Willebrand factor, CD34, and CD8, an antigen which, in man, is expressed only by suppressor/cytotoxic T cells and the endothelial cells of the splenic sinuses. Enzyme-histochemical inv estigations revealed reactivity for nonspecific esterase and lack of r eactivity for alkaline phosphatase - a pattern typical of the sinus en dothelial cells. The tumor could be distinguished from other tumors/tu mor-like lesions of the spleen that exhibit endothelium with character istics typical of the splenic sinuses (peliosis, splenoma, littoral ce ll angioma) on the basis of its histological features. The lack of exp ression of histiocytic antigens by the tumor endothelium is also Evide nce against a diagnosis of littoral cell angioma, which also derives f rom the sinus endothelium. Thus, this tumor could not be identified as any of the recognized tumors/tumor-like lesions of the spleen and it is therefore proposed that it should be designated diffuse sinusoidal hemangiomatosis.