Red and far-red fluorescent dyes for the characterization of head and neck cancer at the cellular level

Background: Primary upper aerodigestive tract malignancy remains a cancer having a poor prognosis, despite current progress in treatment, due to a generally late diagnosis. Objectives: We conducted a preliminary assessment of five dyes approved for human use for the imaging of head and neck tissues at the cellular level, which could be considered for clinical examination. Methods: We investigated fluorescence endomicroscopic images on fresh samples obtained from head and neck surgeries after staining with hypericin, methylene blue, toluidine blue, patent blue or indocyanine green to provide a preliminary consideration as to whether these images contain enough information for identification of non-pathologic and pathologic tissues. The distribution pattern of dye has been examined using probe-based confocal laser endomicroscopy (pCLE) in ex vivo specimens and compared with corresponding histology. Results: In most samples, the image quality provided by pCLE with both dyes allowed pathologists to recognize histological characteristics to identify the tissues. Conclusion: The combination of pCLE imaging with these dyes provides interpretable images close to conventional histology; a promising clinical tool to assist physicians in examination of upper aerodigestive tract, as long as depth imaging issues can be overcome.