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.
Next comes our exercise and nutrition, and then the environment. Of course if you are in a highly toxic present time breathing environment you will want to make it a priority above all others. A common misconception is that 100 years or more, atmospheric oxygen made up 30-40% of the air we breathe. This is simply not true. Researchers at the Scripps Institute tell me there is no atmospheric oxygen shortage.