Electron Paramagnetic Resonance Spectrometry and Imaging in Melanomas: Comparison between Pigmented and Nonpigmented Human Malignant Melanomas

Abstract

It has been known for a long time that the melanin pigments present in normal skin, hair, and most of malignant melanomas can be detected by electron paramagnetic resonance (EPR) spectrometry. In this study, we used EPR imaging as a tool to map the concentration of melanin inside ex vivo human pigmented and nonpigmented melanomas and correlated this cartography with anatomopathology. We obtained accurate mappings of the melanin inside pigmented human melanoma samples. The signal intensity observed on the EPR images correlated with the concentration of melanin within the tumors, visible on the histologic sections. In contrast, no EPR signal coming from melanin was observed from nonpigmented melanomas, therefore demonstrating the absence of EPR-detectable pigments inside these particular cases of skin cancer and the importance of pigmentation for further EPR imaging studies on melanoma.

Research Techniques Made Simple: Cell Biology Methods for the Analysis of Pigmentation

“…In contrast, electron paramagnetic resonance (EPR) spectroscopy discriminates between eumelanins and pheomelanins (Sealy et al, 1982). EPR spectroscopy detects different electron spin signatures from stable free semiquinone-type radicals within the different melanin types, which accurately correlate with pigment concentration (Godechal et al, 2013). EPR analyses can measure eumelanin and pheomelanin ratios even from biological samples such as histological sections (Sealy et al, 1982) but require specialized expertise.…”

Clinical and Biological Characterization of Skin Pigmentation Diversity and Its Consequences on UV Impact

“…EPR is similar to nuclear magnetic resonance in which electron spins are detected instead of nuclear spins. Due to slightly different EPR signals of eumelanin and pheomelanin, this method has been suggested to enable a distinction between both types of melanins in skin or hair samples and pigmented malignant melanomas (for more details see [ 103 ]). However, due to technical limitations this method is not applicable for ex vivo samples and is mostly used for research in the field of melanoma.…”

Medical applications of EPR

“…Ex vivo samples of melanoma have been imaged in the X-band with cw imaging (1024 points in 32.5 min). The comparison with the EPR images and the stained histological samples show a strong correlation between pigmentation and the EPR signal of melanin [34]. Unpigmented samples exhibit no EPR signal.…”