Histopathology of spontaneous lesions in FVB/N mice.

The FVB/N mouse strain is widely used in transgenic studies and as a model for autoimmune diseases. Although spontaneous lesions have been reported in aged FVB/N mice, information regarding younger FVB/N mice is lacking. This study aimed to investigate the spontaneous lesions in young FVB/N mice. Ten males and 10 females were necropsied at 10 and 26 weeks of age. All tissues were fixed in 10% neutral-buffered formalin, embedded in paraffin, and stained with hematoxylin and eosin. Histopathological examination revealed atrophy of the outer retina in all mice of both ages, with atrophy of the inner nuclear layer at 26 weeks. This ocular lesion is consistent with an autosomal recessive disorder in FVB/N mice. Decreased cellularity in the epiphyseal cartilage plate, reduced bone in the primary spongiosa of the femur, increased cellularity of lymphocytes in the thymus, dilatation of ducts in the mammary glands, and foveolar hyperplasia in the stomach were observed, all of which were indicative of age-related changes. These findings provide valuable background data for future studies using FVB/N mice.