GGT1 and neoplasm: In this study, we evaluated the use of gGlu-HMRG for the detection of early HNSCC and found that (1) all HNSCC cell lines examined emitted fluorescence following gGlu-HMRG exposure; (2) HNSCC, but not normal tissue, expressed GGT in three recent ESD cases; and (3) tumor lesions became fluorescent immediately after gGlu-HMRG being applied to all eight HNSCC cases.