Diagnosis of malignant melanoma and basal cell carcinoma by in vivo NIR-FT Raman spectroscopy is independent of skin pigmentation

There is a general need for methods to obtain fast in vivo diagnosis of skin tumours. Raman spectroscopy measures molecular structure and may thus have potential as a tool for skin tumour diagnosis. The purpose of this study was to investigate how skin pigmentation influenced the Raman spectra and skin tumour diagnostics in vivo. We obtained Raman spectra in vivo from the normal skin of 55 healthy persons with different skin pigmentation (Fitzpatrick skin type I-VI) and in vivo from 25 basal cell carcinomas, 41 pigmented nevi and 15 malignant melanomas. Increased skin pigmentation resulted in a higher spectral background caused by fluorescence, which could be removed by background correction. After background correction, we found only a negligible effect of pigmentation on the major spectral bands, and the comparison of the intensity of these bands allowed us to differentiate between normal skin and the different skin lesions independent of skin type. The diagnosis of skin lesions is possible due to significant (p < 0.05) differences found in the water band around 3250 cm(-1), the protein specific band around 1250 cm(-1) (amide-III) and the amide-III ratio that describes the protein/lipid ratio by comparing bands around 1250 cm(-1) with bands around 1300 cm(-1). We have shown that NIR-FT Raman spectroscopy is useable for malignant melanoma and basal cell carcinoma diagnostics in vivo and that pigmentation of the skin or lesion does not influence the diagnosis, but larger data sets are required to establish accurate diagnostic power.