Fax +41 61 306 12 34 E-Mail karger@karger.ch www.karger.com Original Paper Pediatr Neurosurg 2006;42:228–233 DOI: 10.1159/000092359 Aquaporin(s) Expression in Choroid Plexus Tumours Pierluigi Longatti a Luca Basaldella a Enrico Orvieto b Angelo Dei Tos a Andrea Martinuzzi c a Neurosurgery Unit, and b Department of Pathology, Treviso Hospital, Treviso, c E. Medea Scientific Institute, Conegliano Research Centre, Conegliano, Italy pression together with the size of the tumour mass are somewhat predictive of communicating hydrocephalus or liquoral cyst, lesions possibly caused by a disturbance of cerebrospinal fluid homeostasis. Copyright © 2006 S. Karger AG, Basel Introduction Choroid plexus papillomas and carcinomas are rare neoplasms which account for less than 1% of all brain tu- mours; they are mainly located in the lateral and in the fourth ventricle [1–3]. Clinical manifestation is most commonly represented by raised intracranial pressure and more rarely by epi- lepsy or focal neurological deficits [3, 4]. Hydrocephalus is often associated with these malignancies and for 95% of cases it is ascribed to the obstruction of cerebrospinal fluid (CSF) ventricular pathways due to the mass. Con- versely, communicating hydrocephalus is uncommon and has been tentatively attributed to CSF overproduc- tion by the choroid plexus tumour [5–7]. Plexus villous hypertrophy is also remarkably associ- ated with overproductive hydrocephalus, and previous morphological studies showed evidences of CSF hyperse- cretion in the choroid plexus tumour cells [8–10]. The intrinsic mechanism of CSF production in these lesions remains substantially unclear. Aquaporins (AQPs) are selective water channel pro- teins playing a central role in human body water homeo- stasis. In the central nervous system, mainly three AQPs have been identified: AQP1, AQP4 and AQP9 [11, 12] . Key Words Aquaporins  Choroid plexus  Cerebrospinal fluid secretion  Hydrocephalus Abstract Objective: It was the aim of this study to investigate the pattern of aquaporin 1 (AQP1) expression in normal and neoplastic choroid plexus, with specific reference to the association with communicating hydrocephalus or li- quoral cysts. Second, to infer a new view on the cerebro- spinal fluid plexus production and on the etiology of the cysts and communicating hydrocephalus occasionally associated with choroid plexus papillomas. Materials and Methods: Nineteen paraffin-embedded specimens, 10 of normal choroid plexus and 9 of choroid plexus tu- mours, were immunostained with a monoclonal anti- body raised against the intracellular C-terminal AQP1 epitope. Results were analysed in terms of intensity and intracellular distribution of immunostaining and in terms of number of stained cells; they were considered in light of the clinical association with hydrocephalus or liquoral cysts. Results: AQP1 was heavily expressed in the apical side of the choroid epithelium in normal plexus speci- mens. Choroid plexus papillomas showed a very hetero- geneous pattern of AQP1 expression. Immunostaining was absent in the case of choroid plexus carcinoma. Very strong to strong and diffuse AQP1 expression in large to very large papillomas was associated with liquoral cysts or communicating hydrocephalus. Conclusions: AQP1 expression characterizes normal choroid plexus and plexus papillomas. Intensity and diffusion of AQP1 ex- Received: July 13, 2005 Accepted after revision: October 21, 2005 Luca Basaldella, MD Neurosurgery Department, Treviso Regional Hospital University of Padova, Pzza. Ospedale Civile 1 IT–31100 Treviso (Italy) Tel. +39 0422 322506/576, Fax +39 0422 322523, E-Mail lucabasaldella@libero.it © 2006 S. Karger AG, Basel 1016–2291/06/0424–0228$23.50/0 Accessible online at: www.karger.com/pne