Abstract
Hepatic steatosis, also known as fatty liver, is a spontaneous lesion caused by the abnormal accumulation of triglycerides within hepatocytes that has been described in different laboratory-housed nonhuman primate species. Aging is considered a risk factor in the progression of this lesion in humans and captive rhesus macaques. Hepatic steatosis has been reported in sexually mature adult and aged-adult captive common marmosets. Macroscopic changes in the liver may be evident in advanced stages of this condition and are characterized by hepatomegaly with multifocal to coalescing to regionally extensive pale-tan to yellow, soft foci throughout the hepatic lobes. Biochemical abnormalities in these cases include significantly increased levels in triglycerides, insulin, and γ-glutamyltransferase (GGT). Definitive diagnosis is by histopathology and demonstration of lipid accumulation within hepatocytes. Histopathology is characterized by large coalescing areas of periacinar to periportal microvesicular steatosis mixed with clusters of macrovesicular steatosis, and variable degrees of lobular inflammation. Vacuolated hepatocytes containing intracytoplasmic lipid material is demonstrated by positive staining to Sudan IV and/or Oil red-O.