Immunohistochemical features and numbers of argyrophilic nucleolar organizer regions (Ag-NORs) were investigated on 6 cases with
choroid plexus tumors: 3 adult and one pediatric cases with
choroid plexus papilloma (
CPP) and 2 pediatric cases with
choroid plexus carcinoma (
CPC) clinicopathologically. One of the 2 children with
CPC developed a recurrence with dissemination to the CSF and died 2 years postoperatively (case 6), while the other survived following surgery (case 5). This outcome suggested the existence of
biological differences in these
tumors. We conducted an immunohistochemical examination of
prealbumin,
S-100 protein,
glial fibrillary acidic protein (GFAP),
cytokeratin (CKER), and
epithelial membrane antigen (EMA) using
avidin-
biotin complex (ABC) methods and the
silver colloid staining technique for Ag-NORs. All 4
CPP were positive for
prealbumin and
S-100 protein, with 3 of them being strongly positive; 3 of 4 were positive for GFAP and 2 were positive for CKER and EMA. Two cases of
CPC were weakly positive for
prealbumin. However the part of reserved papillary structure of case 5 was strongly positive for it. The
tumor of the survived child was positive for S-100, GFAP, CKER, while negative for EMA. A positivity for
S-100 protein and
prealbumin was associated with a good outcome, whereas that for GFAP, CKER, and EMA was not. The mean number of Ag-NORs in the 2 cases with
CPC exceeded that in cases with
CPP. Of the 2 cases with
CPC, fetal one (case 6) showed a higher number of Ag-NORs than the survived patient.(ABSTRACT TRUNCATED AT 250 WORDS)