SURG-24. QUANTITATIVE ANALYSIS OF TUMOR CELL DENSITY AND PROTOPORPHYRIN IX FLOURESCENCE IN GLIOMA PATIENTS USING PAIRED STIMULATED RAMAN HISTOLOGY AND TWO-PHOTON EXCITATION FLUORESCENCE MICROSCOPY

Abstract Fluorescence guidance is widely utilized to improve the precision of cancer surgery. 5-aminolevulinic acid, most used fluorophore in glioma surgery, thought cause selective accumulation fluorescent protoporphyrin IX (PpIX) tumor cells by exploiting pathologic alterations heme biosynthetic pathways. PpIX-induced fluorescence highly specific for densely tumor-infiltrated tissue but less effective visualizing periphery. To clinical detection PpIX, we developed a microscope perform paired stimulated Raman histology and two-photon excitation microscopy (TPEF) validated it 175 fresh, unprocessed core specimens from 75 high-grade patients three central nervous system lymphoma across institutions. Surprisingly, intracellular PpIX was observed primarily with histiocytic, rather than neoplastic morphology, number concentrating within cytoplasm associated abundance CD163 positive (p< 0.02). There no correlation between degree cellularity concentration all imaged (R=-0.21). Our findings encourage reconsideration existing theory 5-ALA-induced cell gliomas demonstrate how 5-ALA TPEF imaging can provide window into immune microenvironment human gliomas.