Choroid plexus papilloma with osseous and adipose metaplasia

Rare cases of osseous and chondroid metaplasia in choroid plexus papillomas have been described. We report a case of left lateral ventricular choroid plexus papilloma presenting in a 25-year-old man. The tumor demonstrates prominent calcification with associated osseous metaplasia and a region of adipose metaplasia, which has not been previously described in these tumors. There is no evidence of mucin in the papilloma on mucicarmine and alcian blue stains. A MIB-1 labeling index (marker of cell proliferation) of 0.1% was noted. P53 immunoreactivity was not observed in the papilloma. Ann Diagn Pathol 5:43-47, 2001.