Malignant intracranial teratoma in a juvenile Wistar rat.

An intracranial malignant teratoma was identified in a 91-day-old male Wistar rat manifesting central nervous system-related clinical signs. This tumor occupied the right midbrain and portions of the right caudal cerebrum and cranioventral cerebellum. Microscopically, the tumor contained intermingled cartilage, bone (with medullary hematopoietic tissue), fibrous connective tissue, skeletal muscle, fat, pseudostratified ciliated epithelium, stratified squamous epithelium, serous and mucoserous glands, and neural tissue with ependymal and choroid plexus epithelia. Poorly differentiated cells with primitive cartilaginous matrix were present throughout the lining of lateral ventricles, in the aqueduct of Sylvius, and in meninges overlying normal cerebellar tissue indicating tumor metastasis occurred via cerebrospinal fluid. This neoplasm was not identified in extracranial sites and hence was considered a primary intracranial malignant teratoma with metastases via cerebrospinal fluid.