Optical differentiation of lung cancer subtypes using laser absorbance, auto-fluorescence emission and Raman spectroscopy: a case series

Background: Accurate intraoperative localization of small pulmonary nodules remains challenging. Multimodal optical spectroscopy may provide complementary tissue-level information beyond hemoglobin-dependent contrast. This study evaluated multimodal optical differences between lung cancer and paired normal lung tissues. Methods: Twelve patients undergoing surgical resection of primary lung cancer were prospectively enrolled. Paired ex vivo specimens were collected from tumor and normal lung parenchyma. Optical attenuation was quantified at a fixed wavelength of 638 nm and expressed as optical density (OD). Autofluorescence emission and Raman spectra were acquired under identical excitation conditions using a fiber-optic probe-based system. Optical features were compared between tumor and normal tissues and explored by histological subtype. Results: Twenty-four tumor tissues and 24 paired normal lung tissues were analyzed. Tumor tissues exhibited significantly higher optical attenuation at 638 nm than corresponding normal lung tissues in both adenocarcinoma and squamous cell carcinoma, with no significant difference in OD between subtypes. Autofluorescence intensity was consistently lower in tumor tissues than in normal lung tissues, and adenocarcinoma demonstrated higher fluorescence intensity than squamous cell carcinoma. Raman spectroscopy revealed distinct spectral differences between tumor and normal tissues and demonstrated subtype-associated variations, including relatively stronger phenylalanine- and tyrosine-related bands in adenocarcinoma. Conclusions: multimodal optical analysis revealed reproducible tumor-associated differences in optical attenuation, autofluorescence, and Raman spectral features between lung cancer and normal lung tissues. These findings represent tissue-level optical signatures rather than hemoglobin-free intrinsic absorption and support the potential role of multimodal optical spectroscopy as a complementary approach spectroscopic guidance during lung cancer surgery.