Hepatobiliary effects of 90yttrium microsphere therapy for unresectable hepatocellular carcinoma

(90)Yttrium (Therasphere) microspheres administered via hepatic artery are a valuable option for treatment of hepatocellular carcinoma. This therapy targets tumor nodules while largely sparing hepatic parenchyma. This retrospective study examines liver explants from 13 adult patients with hepatocellular carcinoma who received intrahepatic Theraspheres and subsequently underwent liver transplantation. Histopathologic and laboratory reviews are performed. Theraspheres preferentially migrated to the lobe(s) supplied by the injected artery branches and frequently localized to tumors. Tumors showed a chronology of changes beginning with confluent necrosis typically accompanied by hemorrhage and later by fibrinoid change. This was followed by fibrosis with regenerative activity at tumor peripheries. Adjacent hepatic parenchyma went through a similar sequence of injury and repair that could lead to markedly fibrotic cirrhotic nodules in the vicinity of treated tumors. No consistent pattern of thrombomodulin loss was seen in endothelial cells of the tumors or adjacent parenchyma, suggesting that direct endothelial cell injury was likely not a major contributor to the necrotic process. However, the pattern of injury and repair is suggestive of a localized and subclinical form of radiation-induced liver disease. The pathologist should be aware of these changes to distinguish them from the diffuse "radiation hepatitis" associated with older forms of radiotherapy.