Histological study of intrahepatic cavernous transformation in a patient with primary myelofibrosis and portal venous thrombosis.

Cavernous transformation in the liver was examined histologically by serial section observations, in an autopsy case of portal venous thrombosis and primary myelofibrosis. Cavernous transformation was present from the hepatic hilus to medium-sized portal tracts and was composed of dilated and thin-walled vessels. Serial sections disclosed that these vascular channels were anastomotic and occasionally communicated with occluded portal venous radicles. In places they entered directly into the hepatic parenchyma without accompanying biliary or arterial elements, and also drained into the patent portal venous branches beyond the occluded segment. The study demonstrated that cavernous transformation in the liver develops as hepatopetal collaterals secondary to the portal venous obstruction. Periportal and peribiliary capillary plexus may become cavernous in the presence of portal venous occlusion.