Imaging findings of extraventricular choroid plexus papillomas: A study of 10 cases.

Extraventricular choroid plexus papillomas (CPPs) are rare. In this study, we reveal the imaging findings of CPPs located in extraventricular sites. The imaging findings of 11 masses [10 masses on magnetic resonance imaging (MRI) and one mass on computed tomography (CT)] of extraventricular CPP in 10 patients were retrospectively observed. The mass site, size, contour, signal intensity, cystic or solid appearance, calcification, capsules, degree and pattern of enhancement, and hydrocephalus were evaluated based on CT or MRI. The misdiagnosis rate of CPPs in extraventricular sites was 80.0% (8/10). Solitary masses and multiple masses were observed in nine patients (90.0%, 9/10) and one patient (10%, 1/10), respectively. In addition to the typical imaging findings [a lobulated, cauliflower-like or mulberry-like mass that is homogeneous isointense or slightly hypointense on T1-weighted imaging (T1WI) and heterogeneous isointense or slightly hyperintense on T2WI], four masses had round or oval contours and three had cystic components; abnormal signal intensity (mixed hyperintense signals on T1WI and T2WI or slightly hyperintense signals on T1WI or hypo-/hyperintense on T2WI) and low or no enhancements were observed in three and six masses, respectively; absence of hydrocephalus and mild or local hydrocephalus were each observed in four subjects, respectively. Hemorrhage and psammomatous bodies and/or calcification were observed in four and three masses, respectively. In conclusion, in addition to the typical imaging findings, atypical imaging findings, including atypical contours, abnormal signal intensity, low enhancement and absence of hydrocephalus were also observed in extraventricular CPPs.