Clinicopathological study of choroid plexus tumors: immunohistochemical features and evaluation of proliferative potential by PCNA and Ki-67 immunostaining.

This report concerns the retrospective immunohistochemical characterization and evaluation of the proliferative potential of eight choroid plexus tumors (CPTs) that included six cases of choroid plexus papilloma (CPP), one of whom had a recurrence, and two cases of choroid plexus carcinoma (CPC). Antibodies to prealbumin, glial fibrillary acidic protein (GFAP), vimentin, keratin, and carcinoembryonic antigen (CEA) were used to determine the immunohistochemical features of interest. The proliferative potential was evaluated with antibodies to proliferating cell nuclear antigen (PCNA) and Ki-67. Antibody binding was visualized by the avidin-biotin-peroxidase complex (ABC) method. Immunoreactivity was scored on a-to 4+ scale, and in the case of PCNA and Ki-67, expected as staining index (SI). All seven CPP specimens were immunostained for prealbumin, but not for CEA. Expression of GFAP, vimentin and keratin varied from one CPP case to another. Both CPCs expressed CEA, but not prealbumin, GFAP and keratin; one of them was vimentin-positive. As determined by immunostaining for Ki-67, the proliferative potential was lower in the CPPs than in the CPCs. Among the former, the highest Ki-67 SI was seen in the primary lesion of a recurring papilloma. On the other hand, immunostaining for PCNA gave less consistent SI values. Our results show that immunohistochemical assays for prealbumin and CEA expression are of significant value for the differential diagnosis of CPPs and CPCs, and that high Ki-67 SI values may serve as an indicator of CPP recurrence, even if the primary lesion is benign.