Choroid Plexus Tumors

Abstract

While choroid plexus tumors represent less than 1% of CNS tumors overall, they are responsible for a much greater proportion of CNS tumors in the early years of life. Of 170 newborn brain tumors (reported from twelve institutions), 12% were choroid plexus papillomas (CPPs) (1). CPPs preferentially involve the lateral ventricles in children, while the fourth ventricle is most often involved in adults. CPPs have occasionally arisen within the third ventricle (2). Presentation as a cerebellopontine angle tumor is also unusual. In the latter location, CPPs may either arise from the choroid plexus emanating from the foramen of Lushka, extend out from other locations within the fourth ventricle, or represent leptomeningeal dissemination (3). Bilaterality is distinctly unusual, may result in congenital hydrocephalus, has been reported in infants with duplication of chromosome 9p, and is also referred to as hyperplasia or villous hypertrophy of the choroid plexus (4). CPPs usually present with headaches, most often secondary to increased intracranial pressure as a result of excessive CSF production by the overgrown choroid plexus epithelium. Retention of this functional capacity is accompanied by retention of most of the morphologic characteristics of normal choroid plexus epithelium. While the usual cytologic and architectural features of low-grade papillary tumors (overgrowth, crowding, nuclear hyperchromasia and pleomorphism) may or may not be apparent, a fairly reliable feature of CPPs is loss of the normal hobnail appearance of nonneoplastic choroid plexus epithelium (Figs. 18-1 and 18-2). CPPs may, on occasion, demonstrate epithelial variations including tubule formation (5), oncocytic change, and pigmentation (6). Stromal lamellar calcification may frequently be seen within CPPs and may be so heavy as to interfere with tissue sectioning (7).