Choroids plexus papillomas (CPPs) are rare tumors of neuroectodermal origin that account for less than 1% of brain tumors in adults and represent 2-4% of pediatric brain tumors6,18). The most common site of origin in the pediatric age group is within the lateral ventricle, whereas the fourth ventricle is the most common site in adults18). The most important radiologic finding is the intense contrast enhancement, which is homogeneous and shows typical mottled- and cauliflower-like appearance on the edge of tumors in most cases1). Pathologically, these tumors exhibit papillary structures lined by cuboidal epithelium with regular, rounded, centrally-located nuclei and moderate eosinophilic cytoplasm with no evidence of mitosis, necrosis, or anaplasia14). The pathologic papillary growth pattern could explain the cauliflower- and mottled-like appearance radiologically. CPPs are generally regarded as benign tumors with the aforementioned typical radiologic and pathologic findings. However, CPPs sometimes exhibit unusual radiologic findings, which could give the difficulty to diagnose preoperatively. In this study, we reviewed the clinical, radiologic and pathologic findings on our experience.

CPPs account for 0.3-0.7% of all intracranial tumors, 10-20% of brain tumors presenting during the 1st year of life, and 2-6% of tumors in childhood12). These tumors can develop anywhere choroid plexus tissue exists. Generally, the lateral ventricle is the most common site (50% of cases) for these tumors, followed by the fourth ventricle (40%), and the third ventricle (5-9%)10). The site at which CPPs develops is closely linked to patient age. CPPs in younger and adult patients tend to develop primarily in lateral and fourth ventricular lesions, respectively11). The mean age at the time of presentation in our series was 27.4 years (range, 3 months to 59 years). All patients of young age had supratentorial CPPs, whereas patients over 18 years of age had fourth ventricle and suprasellar CPPs. The most common presentation of CPPs is related with the signs due to increased intracranial pressure (ICP)2,9,15). Because these tumors produce cerebrospinal fluid (CSF) in amounts far exceeding the normal average, intraventricular pressure was increased and it causes increased ICP. Hydrocephalus is also well-accompanied because these tumors obstruct the CSF flow mechanically and disturb the CSF absorption at the subarachnoid space secondary to hemorrhage or proteinaceous material. In our cases, there were 6 patients (3/3 in pediatrics and 3/7 in adults) who complained of hydrocephalus-related symptoms.

CPPs showed iso- to hyper-dense intraventricular masses without brain invasion and intense enhancement on CT findings12,17). Calcifications were observed in 24 to 50% of CT images. On MR images, CPPs were iso- to hyper-intense on T1-weighted images and mixed, hypo- to hyper-intense on T2-weighted images1,13). The most important typical radiologic finding in CPPs is the intense contrast enhancement, which is homogeneous and shows typical mottled- and cauliflower-like appearances on the edge of tumors. But all of CPPs do not show these finding. Some minor cases show heterogenous enhancement feature with disappearing the typical mottled like appearance. In our all 10 cases, there were 4 patients with calcified lesions on CT images. On T1- and T2-weighted MR images, the CPPs had variable signal intensities. Seven patients (3/3 in pediatrics and 4/7 in adults) showed typical MR findings which are homogeneous enhancement and mottled-like appearances. There are three patients who had the heterogeneously enhanced mass without mottled-like appearances, which gave the difficulty to diagnose preoperatively. The typical histopathologic pattern of CPPs is the papillary growth of cuboidal epithelium with regular, rounded, centrally-located nuclei and moderate eosinophilic cytoplasm with no evidence of mitosis, necrosis, or anaplasia14,16). On the immunohistochemical staining, the most common CK7/CK20 combination is CK7-positive and CK20-negative in 74%, but the other three combinations are also possible5). In our study, the tumors showed various CK7/CK20 staining patterns and the common pattern was CK7-positive and CK20-negative in 50%. CPPs can show unusual histological features; solid or tubular growth, oncocytic alterations, melanin deposition, calcification, ossification, and xanthograulomatous reaction and mitotic activity is the sole atypical features independently related with the tumor recurrence3,7,8). In our cases, we found three unusual histopathologic growth pattens. Two cases showed the papillary structures combined with a solid growth pattern and one case had the papillary combined with tubular growth pattern. Although these three cases showed the unusual histopathologic findings, they did not have any mitoses and displayed very low Ki-67 proliferation index. These three CPPs with unusual pathologic pattern showed the unusual radiologic findings. Even if the cases were small, we carefully suggested the unusual radiologic findings might be explained with combined growth patterns.

GTR is the first choice in the treatment of CPPs1,4,19) and is considered the most important prognostic factor for CPPs. Because CPPs usually exist in deep brain lesion, surgical treatment targeting the gross total resection sometimes accompanies the adjacent brain parenchymal injuries and causes the complications associated with the site of origin. In our study, pediatric CPPs with preoperative severe hydrocephalus accompanied postoperative hygromas. Two cases adult CPPs with large sized tumor in the fourth ventricle had occurred accompanied brainstem injury in our study and required ventriculoperitoneal shunt procedures for hydrocephalus. Surgical complications occurred in the cases with the severe hydrocephalus or large masses of fourth ventricle.

CPPs could have unusual radiologic findings, which preoperatively give the difficulty to be differentiated from other tumors. CPPs with unusual radiologic findings showed the combined pathologic growth patterns.