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Choroid plexus epithelium (normal and neoplastic) expresses synaptophysin. A potentially useful aid in differentiating carcinoma of the choroid plexus from metastatic papillary carcinomas.

As an incidental finding in paraffin sections of brain tissue used as positive controls for synaptophysin immunostain, the cytoplasm of choroid plexus epithelium present was found to stain strongly positively for this substance. This was subsequently found to be the case in normal choroid plexuses in autopsy material from infancy to old age, as well as in epithelial cells of papillomas and carcinomas of the choroid plexus. The latter findings may prove useful in differentiating choroid plexus carcinomas from metastatic papillary carcinomas of extracerebral origin with the exception of neuroendocrine carcinomas of various sites that are usually positive for synaptophysin.