Choroid plexus papilloma of the third ventricle: case report and review of the literature.

Introduction Choroid plexus tumors (CPT) are defined as papillary neoplasms originating from the epithelium of the choroid plexus within the ventricles. They are classified into mainly two types: -benign choroid plexus papillomas (CPP) (World Health Organization WHO grade I) and -choroid plexus carcinomas (WHO grade III). [1,3] An intermediate group lies between the two groups and is referred to as atypical choroid plexus tumors. However, it is very rare for benign papillomas to convert to carcinomas.[1] Anatomically, the choroid plexus is the junction between the brain pia and the ventricular ependymal layer in all four ventricles [12,13]. Embryologically, it is derived from the specialization of ventricular neuroepithelium along certain neural tube segments. Interestingly, there is a common ontogeny between choroid epithelium and cells of glial origin. On occasion this may create a source of diagnostic confusion. Physiologically, the choroid plexus is specialized in cerebrospinal fluid production [9,10] Choroid plexus tumors are seen in all age groups, with an overall incidence of 0.5% to 0.6% of all brain tumors (10% to 20% in infants). However, they are primarily tumors of childhood with higher incidence rates ranging from 1.8% to 2.9% in the pediatric population. Haddad [16] et al and Galassi [17] et al have reported that choroid plexus tumors constitute 12.8% to 14% of all tumors in infants. Laurence reported that 45% of choroid plexus tumors occur in the first year of life and 74% in the first decade of life. He also concluded that 50% were in the lateral ventricles, 37% in fourth ventricle, 9% in the third ventricle, and the remainder in other locations. There has been no sex predilection shown in many of these studies. They are always solitary tumors. However, rare case reports have been published documenting multiple CPPs. Overall, choroid plexus carcinomas constitute 29% to 39% of all choroid neoplasms. Choroid plexus papilomas are more commonly found in the fourth ventricle in adults.