Liver Disorders

A progressive increase in ploidy (polyploidy) occurs in hepatocyte nuclei with age. The number of chromo­somes may increase to ploidy values of 16 or 32. Thus, karyomegaly, anisokaryosis, polykarya, and cyto­megaly are common incidental findings (Fig.

FIG. 1.117. Liver from an aged B6 mouse with eosinophilic cytoplasmic inclusions in hepatocytes.

present at all ages but increase with age and disease and may be particularly extreme in some GEMs (Fig. 1.118). Hepatocellular fatty change is a normal finding in BALB mice, and the livers of these mice are typically paler than in other strains. One or more foci of hepatic coagulation necrosis in the absence of an infec­tious agent may be observed as incidental findings in many strains of mice. They are probably ischemic in origin. Epithelial hyalinosis and crystals are a frequent incidental finding in the biliary and gall bladder epithe­lium of B6 and 129 mice. Bile ductular proliferation is a common incidental finding in all laboratory rodents and lagomorphs. Proliferation of Kupffer cells and Ito cells can occur under a variety of circumstances but should signal inquiry into the presence of Helicobacter.

FIG. 1.118. Liver from an aged transgenic mouse with cytomegaly, polykarya, megalokarya, intranuclear cytoplasmic invagination, and oval cell hyperplasia.