MALIGNANT SCHWANNOMA OF THE INTRACRANIAL TRIGEMINAL NERVE IN A 19-WEEK-OLD FEMALE SPRAGUE-DAWLEY RAT

Abstract

Light microscopic, histochemical and ultrastructural observations were conducted to examine a spontaneous malignant schwannoma arising from the intracranial trigeminal nerve in a 19-week-old female virgin Sprague-Dawley rat. The tumor, which extended from the right trigeminal ganglia and nerve to the bottom of the cerebellum macroscopically, was composed of sheets of small fusiform cells with rod-shaped nuclei and rather abundant eosinophilic cytoplasms. Some tumorcells were arranged in roughly parallel arrays with nuclear palisades or in a whirling pattern. The tumor had invaded the subarachnoid and Virchow-Robin's spaceof the cerebrum and thoracic spinal cord, and the pars distalis of the pituitary gland. In immunohisto-chemistry, the tumor cells showed positive reaction to anti-S100 protein and anti-vimentin, but were negative for anti-GFAP. Ultrastructurally, interdigitating cytoplasmic processes, a few junctional complexes, and fragmented basal lamina-like structures were observed. These findings closely resembled the malignant schwannoma described in the soft tissues of rats and human. From our review of the literature, we believe our case to be the first report of a spontaneous malignant schwannoma arising in the intracranial trigeminal nerve of a young rat.