Liver - Fatty Change

Fatty change can be focal (Figure 1, arrow; Figure 2) or diffuse (Figure 3, Figure 4, Figure 5, and Figure 6) and macrovesicular (Figure 3 and Figure 4) or microvesicular (Figure 5 and Figure 6). Macrovesicular fatty change is often associated with metabolic disturbances and is generally readily reversible, whereas microvesicular fatty change is more likely a reflection of toxicity, possibly involving mitochondrial disturbances. Figures Figure 1 and Figure 2 represent a focal lesion in which the morphologic features of the vacuolated hepatocytes are consistent with both macrovesicular and microvesicular fatty change. Focal fatty change can be a spontaneous lesion and may be more common in some strains than others, whereas diffuse or zonal (e.g., centrilobular or periportal) fatty change is more likely to be treatment related. The cytoplasmic vacuolization in Figures Figure 3 and Figure 4 is diffuse and consists of both large and small single or double cytoplasmic vacuoles within hepatocytes. The morphologic features are consistent with macrovesicular fatty change, with compression and displacement of the nuclei to the periphery of affected hepatocytes. In contrast, Figure 5 and Figure 6 are representative of microvesicular fatty change, with a more prominent response in periportal and midlobular areas. The cytoplasmic change consists of multiple small vacuoles filling the cytoplasm without prominent compression or displacement of hepatocyte nuclei. Sinusoids may be collapsed by the hypertrophic hepatocytes. Figure 7 and Figure 8 represent a mixture of both macrovesicular fatty change and glycogen accumulation in hepatocytes. Mixtures of glycogen and both macrovesicular and microvesicular fatty change may be seen. Phospholipidosis is another form of hepatocyte cytoplasmic vacuolization that is associated with exposure to cationic amphophilic xenobiotics and requires special staining and/or electron microscopy for definitive confirmation.