DR P. MARAZZI / SCIENCE PHOTO LIBRARY DR P. MARAZZI / SCIENCE PHOTO LIBRARY
Solar keratosis cryotherapy. Image 2 of 2. Liquid nitrogen has been applied to a solar keratosis on the ear of a 70-year-old man. The extreme cold of the liquid nitrogen (-198 degrees Celsius) freezes the keratosis, causing the white areas of dead tissue. The area will heal and the dead tissue will drop off. A solar keratosis, a pre-cancerous growth caused by sun damage, is usually removed in case it turns cancerous. For a sequence showing the treatment of this growth by cryotherapy, see images M729/042-043.
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