Study on the pathogenesis of foreign body granulomatous inflammation in the livers of sprague-dawley rats.

Focal granulomatous inflammation developed in the livers of five 10-week-old male Sprague-Dawley rats. The characteristic features of this lesion were the presence of foreign body multinucleated giant cells engulfing calcium deposits and site-specific development in a fissure formed in a sub-lobation in the left lobe or interlobar fissure of the medial lobe of the liver. To clarify the pathogenesis of this lesion, rat livers showing abnormal sub-lobation or lobar atrophy, rat livers in an acute dermal toxicity study and guinea pig livers in a skin sensitization test were also examined histologically. Consequently, the present lesion was considered to be a reactive change against calcium that was dystrophically deposited in the area of hepatocellular necrosis due to delayed circulatory disturbance caused by external pressure or extension force. Granulomatous lesions like in the present cases should be differentiated from those caused by evident exogenous pathogens such as chemicals or microorganisms.

Spontaneous ganglioneuroma possibly originating from the trigeminal ganglion in a B6C3F1 mouse.

In a carcinogenicity study, a neuronal tumor in the cranial cavity was observed in a 110-week-old female B6C3F1 mouse. At necropsy, the tumor was seen at the site of the pituitary gland. Histologically, the tumor consisted of well-differentiated ganglion cells, nerve fiber/neuropil-like elements and ganglion-like cells. The tumor was composed mainly of ganglion-like cells, which were arranged in solid sheets interspersed with thin fibrovascular stroma. Nissl substance was detected at the margin in the cytoplasm of well-differentiated ganglion cells, and nerve fibers were identified by the Kluever-Barrera method. Immunohistochemically, the well-differentiated ganglion cells were positive for S-100, neurofilament protein (NF), neuron-specific enolase (NSE), synaptophysin, and chromogranin A. The nerve fiber/neuropil-like elements were positive for S-100, NF, NSE, and glial fibrillary acidic protein (GFAP), and the ganglion-like cells were strongly positive only for NSE and synaptophysin. On the other hand, there were no pituitary cells, such as prolactin-positive or adrenocorticotropic hormone (ACTH)-positive cells in the tumor tissue. Detailed histopathological examination suggested that the tumor might be a ganglioneuroma arising from the trigeminal ganglion. This report provides additional histopathological evidence of peripheral nerve neoplasms in mice.