Extraventricular choroid plexus papilloma in the brainstem.

Choroid plexus papilloma (CPP) is extremely rare in the brainstem. The authors report the case of a 10-year-old boy with a lesion in the pons that was misdiagnosed as a glioma preoperatively. The boy underwent partial resection of the lesion, which was diagnosed as a CPP based on histopathological findings. The authors review the MRI findings in this case and conclude that the presence of a well-defined boundary and no obvious cerebral edema are valuable features for distinguishing brainstem CPP from glioma. Although previous reports of parenchymal CPPs have described enhancement on contrast-enhanced T1-weighted MR images, the lesion in this case did not demonstrate significant enhancement. The authors note that the diagnosis of extraventricular CPP cannot be ruled out in a case of brainstem tumor without marked enhancement.