ESR investigation of paraffin-embedded ocular melanomas

Ocular melanomas embedded in paraffin wax for histological examination have been studied by electron spin resonance (ESR) spectroscopy. A free-radical signal was detected at the g = 2.003 section of the spectrum. The amplitude of this signal was correlated with the number of melanin granules in microscopical slides made from the tumour. This positive correlation can make ESR spectroscopy suitable for estimating the melanin content in the embedded melanoma blocks. Additional paramagnetic signals can also be detected. The clarification of their significance needs, however, further ESR measurements.