Analysis of skin neoplasms' Raman spectra using the Lorentz approximation method: pilot studies

Confocal Raman microspectroscopy provides the ability to diagnose cancer by quantitatively analyzing spectral features and identifying underlying biochemical changes. The differentiation of malignant skin neoplasms (basal cell carcinoma, squamous cell carcinoma), benign skin neoplasms (papilloma) and healthy skin was carried out by obtaining Raman spectra in vitro with excitation wavelengths of 532 and 785 nm. We present a new method for analyzing the parameters of spectral bands, based on the calculation of the second derivative and Lorentz approximation of the spectra. Using this method on a small selection of skin tumors, we have demonstrated that processes in skin tumors can cause deformation of the proteins' secondary structure, leading to degradation and shift of the corresponding bands (972, 1655 cm$^{-1}$) to the lower frequency. Bands corresponding to lipids in skin neoplasms either broaden and increase or split into two peaks (bands 1061, 1127, 1297, 1439, 1745 cm$^{-1}$). The disruption of lipid structure, also indicated in several bands as a shift to lower wavenumbers, is possibly due to increased cell membrane fluidity in tumors. The results of the study may be useful for the development of optical biopsy methods for early diagnosis of tumors.