Inflammatory lesion mimicking a metastatic ependymoma.

A 2.5-year-old child who had undergone nearly total resection of an infratentorial ependymoma demonstrated a new enhancing lesion on the undersurface of the right cerebellar hemisphere 7 weeks after the initiation of adjuvant chemotherapy. The residual primary tumor demonstrated continued regression during chemotherapy, and magnetic resonance imaging of the spine and cytopathological examination of the cerebrospinal fluid showed no evidence for other sites of metastatic tumor. Because of the unusual anatomic and temporal characteristics of this lesion and despite radiographic criteria highly suspicious for a metastatic lesion, a biopsy was performed, revealing histological evidence of an inflammatory process.