LAUSR

Ovarian mature teratomas frequently contain central nervous system (CNS) tissue that often exhibits a variety of neuropathologic alterations. The author systematically examined the changes seen in CNS tissue from a series of 251 cases of resected ovarian mature teratomas. A total of 101 (40.2%) samples contained CNS tissue in varying amounts. The principal pathologic findings in the CNS tissue from ovarian mature teratomas were as follows: (i) CNS tissue tended to form a relatively thin, undulating, plate‐like structure that comprised the walls or septa of cystic tumors; (ii) most neurons were small or medium sized, and no CD34‐positive “ramifying cells” were observed; (iii) cytoplasmic processes of some astrocytes closely surrounded the walls of capillaries, suggesting formation of a blood–brain barrier; (iv) some ependymal cells exhibited a columnar shape and showed a pseudostratified arrangement, and these cells extended thick basal cytoplasmic processes into the neuropil; (v) a few choroid plexus epithelial cells showed melanin deposition, tubular transformation, or oncocytic changes; (vi) hamartoma‐like hyperplasia of arachnoid cells was noted beneath skin tissue; (vii) some CNS tissue showed formation of cerebral cortical structures exhibiting “gyration” with incompletely layered structures, and disruption of the glia limitans with spillage of cortical tissue into the “subarachnoid” space was also observed; and (viii) in the well‐formed cerebellar cortex, dendrites of Purkinje cells exhibited varied dysmorphic changes. These neuropathologic observations should lead to a deeper understanding of the pathogenesis of various lesions in the brain.