SPONTANEOUS MALIGNANT CRANIOPHARYNGIOMA IN AN ALBINO-RAT

Craniopharyngioma is a rare neoplasm in the rat, and few cases have be en described. These Lesions are thought to originate from squamous cel l remnants of Rathke's pouch, an evagination of primitive stomatodeum. This neoplasm is usually locally invasive, and neither cranial nor ex tracranial metastases have been described. A spontaneously occurring m alignant, metastasizing craniopharyngioma arising from the neurohypoph ysis was detected in a 2-year-old male albino rat. The infiltrative gr owth was observed in the wall of the vessels of the circle of Willis, in the perivascular space of Virchow and Robin, in the submeningeal sp ace near the hypothalamus, through the fissura chorioidea, in the medu lla oblongata, and along the optic nerve into the periocular region. M etastases were detected in the thalamus and hippocampus, The diagnosis was made on the basis of microscopic, immunocytochemical, and ultrast ructural findings.