Is stereotactic biopsy a reliable method to differentiate tumor from radiation necrosis?

We report a case of a 37-year-old female who suffered from seizures and underwent external beam radiotherapy due to a suspected low-grade astrocytoma in the left hemisphere. After 7 years free of seizures under antiepileptic treatment and no signs of change in the yearly performed control MRI, she developed a progressive right-sided hemiparesis. MRI now showed an enhancing lesion with space occupying perifocal edema in the entire left hemisphere. Stereotactic biopsy revealed only inflammation. Due to further progress of the neurological deficit an open biopsy was performed. Histological examination revealed a middle-graded astrocytoma and a radiation necrosis. This case demonstrates that radiation necrosis and tumor recurrence may develop concurrently and that it may be difficult to distinguish them by clinical or radiological methods.