FTIR microspectroscopy of melanocytic skin lesions: a preliminary study

Abstract

Fourier transform infrared (FTIR) microspectroscopy has been employed to investigate benign (ordinary dermal and Reed nevi), dysplastic and malignant (invasive melanoma) skin lesions through the analysis of spectral changes of melanocytes as well as in the evaluation of the presence of melanin. Hierarchical cluster analysis and principal component analysis led to a satisfactory separation of malignant from dysplastic and normal melanocytes. Also, on enlarging the clustering with spectra from Reed and dermal nevi, the multivariate analysis segregated well the spectral data into discrete clusters, allowing the obtaining of reliable average spectra for analysis at the molecular level of the main groups or components responsible for the biological and biochemical changes. The most significant spectral characteristics appear to be related to differences in secondary protein structures, in nucleic acid conformation, in intra- and intermolecular bonding. In all cases, supervised and unsupervised spectral analyses resulted in satisfactory agreement with histopathological findings.

FTIR microspectroscopic characterization of Spitz nevi

“…Likely to the histopathological analysis, which reported an extremely homogeneous tumoral morphology for malignant melanoma (MM), composed by melanocytes and melanin granules, the UHCA procedure resulted only into two clusters (blue and red) slightly differing in the Amide II component bands (similarity: 70%) (Fig. 1b 0 ) [22]. The classic Spitz nevus (CSN) is classified as an atypical, but benign lesion, characterized by melanocytes with large nuclei, prominent nucleoli, and abundant ground-glass cytoplasm with polygonal (epithelioid) and often also cigar shaped (spindle) outlines [29,30].…”

“…Melanocytes were separately analyzed because their morphology and biochemical composition (such as melanin amount) strongly characterize the different skin lesions [22]. The raw spectra of control (Cm), malignant (Mm), classic (CSm), desmoplastic (DSm) and atypical (ASm) spitzoid melanocytes, were successfully submitted to HCA and PCA analyses, to identify significant spectral features of each specimen.…”

“…For each map, the number of spectra ranged from 3000 to 6500. Background scans were acquired and ratioed against the sample spectrum [22]. Atmospheric compensation (CO 2 and water vapor subtraction) was applied to raw spectra before data analysis.…”

“…Before infrared analysis, all the sections were de-waxed by immersion in fresh xylene (4 min) and then washed in absolute ethanol (4 min) [22,[26][27][28].…”

“…This analytical technique has received a great attention from medical community, including dermatologists, for the high accuracy in monitoring the structural changes in normal and diseased samples (biological fluids, cells and tissues) [18,19]. At the better of our knowledge, there are only some contributions describing the use of IR and Raman spectroscopies to analyze skin cancerous lesions [20][21][22], but none concerning spitzoid lesions.…”