Neoplasm of hepatic stellate cells (spongiotic pericytoma): a new tumor entity in human liver.

The purpose of this investigation was to classify a previously unknown tumor entity in human liver observed in a 35-year-old woman. It was characterized by an unusual accumulation of fusiform CD34-positive cells and was initially misconceived as a tumor of the liver sinusoids. The tissue was examined by light and electron microscopy and by immunocytochemical techniques with a broad spectrum of antibodies. The polycyclic tumor contained multiple nodular cell aggregates. The tumor cells possessed extensive cytoplasmic processes, rough endoplasmic reticulum, a prominent Golgi complex, and, in isolated cases, fat droplets. They expressed vimentin, CD34, CD105, CD99, CD56, and sm-actin. The matrix surrounding these cells was reactive for collagen types I, III and V, and fibronectin. The unusual aspect of this tumor is that it contained collections of cells that appeared to be hepatic stellate cells (Ito cells). It also contained hepatic cells arranged in plates, lobules, and capillarized sinuses. These findings suggest that the tumorous proliferation of hepatic stellate cells is functionally linked to the hepatocytes. It is unclear whether there is a link between the tumor and the patient's use of oral contraceptives. Referring to animal studies, different hepatocarcinogens may cause neoplastic Ito cell proliferation. The patient has remained recurrence-free during the 12 months since operation.