Skin examination. Dermatologist examining the skin on a woman's face with a SIAscope II machine. This machine is used to detect malignant melanoma skin cancers. It passes different wavelengths of light into the skin and uses the quantity of reflected light to build a picture of the underlying tissue, which is displayed on a screen. Malignant melanomas arise from the skin's melanocytes, the cells that produce the pigment (melanin) that give skin its colour. The main cause of melanoma is exposure to ultraviolet radiation in sunlight. It is an aggressive cancer and early detection can greatly improve a patient's prognosis. The SIAscope II is produced by Astron Clinica.