Spectrophotometric imaging of cutaneous pigmented lesions: discriminant analysis, optical properties and histological characteristics.

Reflectance imaging spectroscopy at 17 selected wavelengths in the range 420-1040 nm has been applied as a method to discriminate melanoma from other pigmented cutaneous lesions. Reflectance images are acquired for 18 primary melanomas and 33 benign naevi in 44 patients. From each spectral image, four parameters related to lesion reflectance (mean value of reflectance, variegation, area and roundness of lesion) are derived at the corresponding wavelength. A discriminant function between the two groups of lesions is determined by using a stepwise discriminant analysis, resulting in a test with a sensitivity of 89% and a specificity of 88%. Since analyses are carried out on the same data set used to obtain the discriminant function, our results should be interpreted with caution. Moreover, in an attempt to assign a physical and/or physiological meaning to the lesion image descriptors, some histological features (i.e., lesion thickness, degree and uniformity of pigmentation) have also been analysed, and their correlations with the image descriptors investigated. Neither degree nor uniformity of pigmentation can fully explain the variations observed in the lesion image descriptors. It is hypothesized that the presence of pathologically related biological components such as lymphocytes and highly aggregated cells may play an important role. The actual performance of the spectrophotometric imaging system should be proven in an additional, unselected number of cases before being used as a diagnostic adjunct for physicians in the clinical detection of melanoma.