gms | German Medical Science

Objective: To establish an intraoperative technique to differentiate tumor from healthy tissue we used confocal laserendomicroscopy (CLEM) without fluorescence in tumor patients. In addition confocal laserendomicroscopy was performed in murine cerebrum and cerebellum to show typical architecture

Method: Tumor samples of 16 gliomas (2 WHO II, 3 WHO III, 11 WHO IV), 12 meningioma WHO I, 3 metastases, 2 cavernoma, 1 hemangiopericytoma WHO II and 1 hemangioblastoma WHO I-II were examined ex vivo but immediately after resection and before analysing them by conventional histopathology. Overall 27804 images with a lateral resolution of 2 µm and a field of view of 300x300 µm were collected. CLEM and histological sections were collated. Moreover CLEM was performed on cerebral cortex, white matter, corpus callosum and cerebellum of fresh mouse brain.

Results: In patients with high-grade glioma and metastases normal brain tissue, infiltration zone, vital tumor cells and necrosis were detected reproducible using CLEM. WHO criteria such as cell density, microvascular proliferation and necrosis could be visualized. A differentiation of metastases vs. glioblastoma was difficult but the differentiation to normal brain tissue was obvious. Collagen patterns, calcifications and psammoma bodies were represented consistently in meningeoma and correlated to histopathology. Images of murine cerebellum showed typical features such as molecular layer, purkinje cell layer and granule cell layer. Neural tracts in corpus callosum and white matter as well as typical aspects of cortex could be identified reliably.

Conclusions: Non-fluorescence CLEM facilitates a distinction of brain structures and tumor tissue. Thus it is possible to detect infiltrative brain tumor margins and characteristics like cell density during surgery. Since no contrast media (fluorescence) is required in vivo application of this technique is very easy. It may help to get an immediate intraoperative feedback for differentiation normal vs. pathological tissue without the delay of standard frozen section analysis thus speeding up intraoperative decision making and ensuring that the desired extent of resection is achieved.