Cicatricial Fibromatosis Mimics Metastatic Medulloblastoma

Axial spin-echo MR images in a 15-year-old boy acquired 8 months after surgery for cerebellar medulloblastoma.

A, T1-weighted image (600/15/2 [TR/TE/excitations]) shows an isointense small round mass (arrow) under the right semispinalis capitis muscle.

B, On T2-weighted image (3000/90/1), the mass (arrow) is well demarcated and isointense relative to subcutaneous fat.

C, On postcontrast T1-weighted image (600/15/2), the mass (arrow) enhances markedly and homogeneously.