Kidney cancers can be cystic, and differentiating between a single benign cyst of the kidney and a kidney cancer can occasionally be a problem. When many cysts are present, as in polycystic renal disease, the distinction is easier. Cysts may also be caused by some parasitic infections.
It will actually collect the oxygen in the ambient air (~21%) and convert it into a concentration of around 85-94%. One of the main reasons you would want a concentrator over a tank and regulator would be when you are using a lot of oxygen for taking ozone saunas or ozonating oils.
What are the three main gases in the air? The three main gases found in the Earth's air are nitrogen, oxygen and water vapor. A typical volume of air at sea level at 15 degrees Celsius contains approximately 78 percent nitrogen, 21 percent oxygen and between 1 and 5 percent water vapor.