Pediatric atypical choroid plexus papilloma: Clinical features and diagnosis

Atypical choroid plexus papilloma (aCPP) is a newly introduced subtype of choroid plexus tumors (CPTs) defined by the World Health Organization (WHO) in 2007 and is characterized by intermediate characteristics between choroid plexus papilloma (CPP) and choroid plexus carcinoma (CPC). Currently, the available data describing the clinical features of aCPP in children are limited.

We performed a retrospective review of 24 pediatric patients with CPTs in our institute and focused on the clinical, radiological and histopathological features of 9 patients with aCPP.

The median age of aCPP patients was 12 (3-144) months, which was younger than the age of CPP patients (36 (5-132) months, P < 0.05). Of the 9 aCPPs, there were 4 cases of giant masses in the cerebral hemisphere, which was significantly higher than that in CPPs (44.4 % vs 0.0 %, P < 0.05). According to MRI analysis, cysts and necrosis (66.7 % vs 16.7 %, P < 0.05), peritumoral edema (55.6 % vs 8.3 %, P < 0.05) and blurred borders (55.6 % vs 8.3 %, P < 0.05) were more common in aCPPs than in CPPs. T1WI isointense signals were mainly observed in aCPPs and CPPs (aCPP66.7 % vs CPP58.3 %, P >0.05), while T2WI slightly low signals were more common in CPPs (CPP41.7 % vs aCPP0%, P < 0.05); moreover, the tumor volume of aCPPs was significantly larger than that of CPPs (aCPP78.3 cm3 vs 8.4 cm3, P < 0.05). For the DWI sequence scans, isointense signals were more common in aCPPs (aCPP77.8 %>CPP25.0 %, P < 0.05), while slightly low signals were more common in CPPs (CPP58.3 %>aCPP0%, P < 0.05). Both aCPPs and CPPs mainly showed homogeneously strong enhancement (aCPP66.7 % vs CPP91.7 %, P > 0.05). Interestingly, 1 aCPP showed annular enhancement. For the pathological and immunohistochemical studies, the Ki67 proliferation index was significantly higher in aCPPs than in CPPs (13 % vs 6%, P < 0.05), and the S-100(+)/Vim(+)/Syn(+) positive rate was higher in aCPPs (58.3 % vs 11.1 %, P < 0.05).

aCPP shows some distinctive clinical features compared with CPP, such as younger age, larger tumor size, more frequent necrosis and peritumoral edema, blurred borders, slightly low signals on T2WI and isointense signals on DWI, and a higher S-100(+)/Vim(+)/Syn(+) positive rate, which may provide more valuable evidence for differential diagnosis and clinical decisions surrounding aCPP.