Background Atypical choroid plexus papilloma (APP) is a rare, newly introduced entity with intermediate characteristics. To date, few reports have revealed the magnetic resonance (MR) findings. Purpose To analyze the clinicopathological and MR features of APP. Material and Methods The clinicopathological data and preoperative MR images of six patients with pathologically proven APP were retrospectively reviewed. The MR features including tumor location, contour, signal intensity, degree of enhancement, intratumoral cysts, and necrosis; and flow voids, borders, peritumoral edema, and associated hydrocephalus were analyzed. Results The APP were located in the ventricle (n = 4) and cerebellopontine angle (CPA, n = 2). Tumor dissemination along the spinal subarachnoid space was found in one patient. The tumors appeared as milt-lobulated (n = 5) or round mass (n = 1), with slightly heterogeneous signals (n = 5) or mixed signals (n = 1) on T1-weighted and T2-weighted images. Heterogeneous and strong enhancement were found in five cases on contrast-enhanced images. Three of four intraventricular tumors had a partly blurred border with ventricle wall. Four tumors had mild to moderate extent of surrounding edema signals. A slight hydrocephalus was seen in four patients. Incomplete capsule was seen in four tumors at surgery. Histopathologically, mild nuclear atypia was seen in all tumors with a mitotic rate of 2-5 per 10 high-power fields. Conclusion APP should be included in the differential diagnosis when an intraventricular or CPA tumor appearing as a multi-lobulated solid mass with slight heterogeneity, heterogeneous strong enhancement, partly blurred borders, mild to moderate peritumoral edema, or slight hydrocephalus are present.
Abstract. 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.
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