Pathological correlation of CT ring in recurrent, previously treated gliomas

The meaning of the enhancing ring commonly seen on computerized tomographic (CT) scans in patients with recurrent, treated glioblastoma has long been of concern. Does the ring represent radiation necrosis, pseudocapsule formation, compressed adjacent brain, or, in fact, a peripheral zone of viable tumor? We employed a multiple intratumoral biopsy technique at the time of reoperation to investigate this ring. Pathological evidence is presented documenting the content of the ring to the viable tumor. It is suggested that perhaps treatment failure may be determined on sequential CT examinations by comparing the volume and degree of contrast enhancement.