AGE AND THE RISK OF ANAPLASIA IN MAGNETIC RESONANCE-NONENHANCING SUPRATENTORIAL CEREBRAL-TUMORS

BACKGROUND. It is often assumed that a cerebral lesion that is nonenha ncing on a magnetic resonance imaging study with gadolinium contrast i s a low grade tumor. Some physicians recommend observation rather than biopsy for such lesions. METHODS. The authors prospectively evaluated the incidence of anaplastic tumor histology in a consecutive series o f patients who presented to a neuro-oncology service with a nonenhanci ng mass of the cerebral hemisphere. RESULTS. During a 5-month period, the authors evaluated 31 patients who had a nonenhancing lesion in the cerebral hemisphere on initial magnetic resonance images. Thirty pati ents underwent stereotactic biopsy (27%) or open resection (73%). The median patient age was 36 years (range, 6-63 years). There was no mort ality or permanent neurologic morbidity from surgery. Twenty-eight pat ients had pathologic confirmation of diagnosis while their lesions wer e still nonenhancing. Of these patients, 9 (32%) had Grade 3 lesions ( anaplastic astrocytoma or oligoastrocytoma), 13 (43%) had Grade 2 lesi ons (astrocytoma, oligodendroglioma, or oligoastrocytoma), and 2 (7%) had Grade 1 lesions (dysembryoplastic neuroepithelial tumors). Two add itional patients (ages 33 and 59 years) who developed enhancement with in their lesions during preoperative periods of observation had gliobl astomas at surgery. Logistic regression was used to relate patient age to the risk of anaplasia in a nonenhancing cerebral mass lesion. Olde r age predicted a significantly higher risk of anaplasia (P = 0.025). The model predicted that nonenhancing cerebral masses in patients olde r than 44 years were more likely to be anaplastic tumors than low grad e tumors. There was no ''safe'' age below which low grade histology co uld be confidently assumed. CONCLUSIONS. Magnetic resonance-nonenhanci ng cerebral lesions may be histologically anaplastic, even in young pa tients. The risk of anaplasia in magnetic resonance-nonenhancing lesio ns increases significantly with patient age. (C) 1997 American Cancer Society.