The choroid plexus carcinomas of childhood: histopathology, immunocytochemistry and clinicopathological correlations.

Anaplastic choroid plexus carcinoma is a tumour with a predilection for the posterior fossa of infants and can be difficult to distinguish histologically from medulloblastoma without the aid of immunocytochemistry using a panel of antibodies. Of a series of 17 choroid plexus carcinomas (five of which were classed as moderately differentiated and 12 as anaplastic) 17 expressed antigens to transthyretin, transferrin and cathepsin and 16 expressed carbonic anhydrase II. Eleven expressed at least one epithelial marker (cytokeratin or epithelial membrane antigen). In contrast, none of six medulloblastomas expressed epithelial markers, transrythetin, carbonic anhydrase II or transferrin, though three were positive with antibodies to cathepsin.