Frameless stereotactic-directed tissue sampling during surgery of suspected low-grade gliomas to avoid histological undergrading

Detection of anaplastic tumor foci for precise grading of gliomas is crucia l for prognostic assessment and appropriate postoperative treatment plannin g. To avoided under-grading in large suspected low-grade gliomas, we employ ed frameless sterotaxy during open surgery for tissue sampling of radiologi cally suspected anaplastic foci. In nine patients (mean age 44 years, range 10-67) with large supratentorial suspected low-grade gliomas (32.4 ccm mea n vol, range 17.9-68.6 ccm) with small contrast enhancing areas (7.7% mean of total volume, range 0.7-15.3%), a neuronavigation system with a pointer device (Easy Guide System Philips) or a navigating microscope (MKM System Z eiss) was used to target small enhancing tumor parts for cytological invest igation during open surgery. Consecutive cytological smears revealed anapla stic tumor foci in all patients, correlating with neuroradiologically demon strated small contrast enhancing areas, although biopsies from all other tu mor parts showed low-grade tumors. Final neuropathological diagnosis confir med anaplasia within the neuroradiologically suspected low-grade gliomas in all patients (2 grade IV, 5 WHO grade III and 2 grade II-III tumors, WHO c lassification). In our experience frameless stereotactic-directed intraoper ative tissue sampling during open surgery of large suspected low-grade glio mas helps to identify small anaplastic areas in mostly large low-grade tumo rs, and therefore, permits optimum planning of postoperative treatment.