Livers have solitary or multiple small, irregular, light brown foci that may coalesce . No pathogenic bacteria have been isolated nor have antibodies to mouse pathogens been detected in routine serological surveys of colonies or evaluation of individuals with hepatic lesions. The foci are sharply demarcated. Scattered individual hepatocellular necrosis may also be seen in livers with prominent foci of necrosis. Cytoplasmic borders are evident.
Chronic lesions exhibit various degrees of peripheral fibrosis.
Thrombi can occasionally be identified in adjacent vessels, but extensive serial sectioning may be necessary to identify vascular lesions. No pathogenic organisms have been identified in any of the cases diagnosed at The Jackson Laboratory using a variety of special stains including Warthin-Starry, tissue Gram, Gomori's methenamine silver, Steiner's, or Giemsa stains. The pathogenesis of focal hepatic necrosis in inbred laboratory mice appears to be ischemia secondary to vascular occlusion, usually a thrombus in a vessel supplying blood to the affected area. Several strains of mice have a propensity for developing auricular mural thrombi, 2-4 which may be the source of emboli that ultimately lodge in the liver. Comparison to Helicobacter Associated Liver Lesions Scientists at NIH have recently reported infection in their colonies with a new Helicobacter-like organism that causes focal hepatic necrosis, mild nonsuppurative inflammation, oval cell hyperplasia, hepatomegaly, bile duct hyperplasia, and peribiliary leukocyte infiltrates.