Pediatric atypical choroid plexus papilloma reconsidered: increased mitotic activity is prognostic only in older children

Excerpt

Choroid plexus tumors are intraventricular tumors that represent 3 % of central nervous system tumors in children and adolescents [5], but 10–20 % of brain tumors occurring throughout the first year of life [6]. According to the World Health Organization (WHO) classification, choroid plexus tumors can be divided into choroid plexus papillomas (CPP, WHO grade I), atypical choroid plexus papillomas (aCPP, WHO grade II) and choroid plexus carcinomas (CPC, WHO grade III) [6]. While CPC show histopathological signs of malignancy and distinct molecular features [4, 7, 8], CPP are benign papillary neoplasms closely resembling non-neoplastic choroid plexus. The observation that increased mitotic activity (≥2 mitoses/10 high power fields) was associated with a higher probability of recurrence in CPP affecting children and adults [2] resulted in the current WHO definition of aCPP, i.e., CPP with increased mitotic activity [3]. In a subsequent pediatric cohort, aCPP did not have significantly worse progression-free survival when compared with CPP [9]. In the latter series, however, patients harboring atypical CPP were younger than in the first study [2], raising the possibility that increased mitotic activity might not have an adverse prognostic effect in younger children. Indeed, two recent studies suggested that CPP and aCPP in younger children show not only similar molecular profiles, but also comparable outcome [1, 4]. These results are questioning the concept of aCPP, but might well be related to an age-dependent effect. We thus aimed to investigate the prognostic value of increased mitotic activity in pediatric CPP and aCPP according to age. …