Atypical choroid plexus papilloma
Atypical choroid plexus papillomas are WHO grade II tumours derived from choroid plexus epithelium with intermediate clinical and pathological features between the much more common, and more indolent, WHO grade I choroid plexus papilloma and the more aggressive WHO III choroid plexus carcinoma.
As clinically, and on imaging, they are difficult to distinguish from choroid plexus papillomas and therefore their description is not repeated here.
Atypical choroid plexus papillomas are distinguished from choroid plexus papillomas primarily on the basis of increased mitotic activity (≥2 mitoses per 10 high-power fields; choroid plexus carcinomas have ≥5 mitoses per 10 high-power fields) 1.
Other features that may be present include 1:
- increased cellularity
- nuclear pleomorphism
- more solid growth pattern with blurring of papillary pattern
- 1. Louis DN, Ohgaki H, Wiestler OD, Cavenee WK "WHO Classification of Tumours of the Central Nervous System. 4th Edition Revised" ISBN: 9789283244929