Object: Malignant progression of choroid plexus papillomas has been occasionally reported, but this issue has not yet been systematically addressed.
Methods: Frequency and extent of malignant progression were examined in a retrospective series of 124 primary choroid plexus papillomas using uniform histological criteria.
Results: After gross-total resection and a mean follow-up period of 59 months, 12 recurrences necessitating neurosurgical intervention had occurred in the 103 cases of choroid plexus papilloma (World Health Organization [WHO] Grade I) and 21 cases of atypical choroid plexus papilloma (WHO Grade II). The proportion of recurring tumors was higher in cases of atypical choroid plexus papilloma than in cases of choroid plexus papilloma (six [29%] of 21 compared with six [6%] of 103, respectively; p < 0.05). In the majority (10 of 12) of the recurrences, there was a close correspondence between the primary tumor and the recurrence with respect to features identified on routine histological examination as well as Ki 67 (MIB-1) proliferation indices (median value 4% for both primary and recurrent tumors; range 0-15% for primary compared with 0-12% for recurrent tumors). However, two patients experienced a transition from a choroid plexus papilloma (WHO Grade I) and an atypical choroid plexus papilloma (WHO Grade II) to choroid plexus carcinomas (WHO Grade III).
Conclusions: Recurrent tumor growth after gross-total resection is rare in choroid plexus papillomas, but malignant progression to choroid plexus carcinoma does occur in a small percentage of tumors.