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S-antigen immunoreactivity in tumors of the choroid plexus.

Using monoclonal antibodies (MAbs) directed against retinal S-antigen, the authors demonstrated the presence of S-antigen immunoreactivity in six of six (100%) tumors of the human choroid plexus, a tissue rich in β-adrenergic receptor activity. An anti-retinal S-antigen MAb F4C1, showed S-antigen immunoreactivity in one papilloma of the choroid plexus and in five of five (100%) carcinomas of the choroid plexus. In contrast, a papillary ependymoma of the spinal cord, an astrocytoma, an oligodendroglioma, metastatic oat cell carcinoma and metastatic adenocarcinoma to the brain did not stain. Our study indicates that MAb F4C1 may prove to be a useful immunohistochemical marker of tumors originating from the choroid plexus.