Choroid plexus carcinoma in siblings: a study by light and electron microscopy with Ki-67 immunocytochemistry.

Choroid plexus carcinomas in siblings aged 11 months and 10 years were examined by light microscopy and immunocytochemistry. One case was studied by electron microscopy. Choroid plexus carcinoma is rare, with approximately 24 reported cases in children. Predicting the behavior of choroid plexus tumors from the histology can be difficult. Neither mitoses nor necrosis were seen in one case, but evaluation of proliferation using Ki-67 monoclonal antibody showed 9% of the cells to be in proliferative phases of the cell cycle, a high value for a glial-derived neoplasm. Ki-67 activity may be a more sensitive measure of proliferation in malignant choroid plexus tumors than the presence of mitoses and necrosis, and additional studies may establish its role in distinguishing between choroid plexus carcinoma and papilloma when histologic classification is equivocal. Both tumors were immunoreactive for keratin, which confirmed previous studies. Both were nonreactive for glial fibrillary acidic protein, S-100, and carcinoembryonic antigen (CEA), unlike a previous study which reported that choroid plexus carcinoma, compared to papilloma, was uniquely S-100-negative and CEA-positive. Choroid plexus carcinoma in siblings has not been reported. Chance occurrence in siblings is extremely unlikely; thus a genetic basis for the neoplasms is likely, although environmental influences cannot be excluded.