Background: The case of a left temporoparietal choroid plexus papilloma in a 12-year-old girl, which recurred 12 months after subtotal resection and apparent full recovery, is described.
Methods: The two consecutive surgical specimens were studied by light and electron microscopy.
Results: The first surgical specimen showed a tumor composed of cells with distended cytoplasm packed with numerous mitochondria characteristic of "oncocytic" change. Thus, tumor was the rare benign oncocytic variant of choroid plexus papilloma. A repeat histologic study of the recurrent tumor 12 months later showed evidence of malignant evolution in the form of multinucleated cells with frequent, often bizarre, mitotic figures.
Conclusion: A rarely described oncocytic variant of choroid plexus papilloma that showed evidence of evolution from benign to malignant "oncocytoma" is discussed.