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.
In Prehistoric Park Edit. On site, Upper Carboniferous air is 35% oxygen, not 20% as now, and that is why the insects are so big. Nigel climbs a 150-foot-tall tree (Sigillaria or Lepidodendron or similar): it has no branches until near its top, and he must use a loop of strap around himself and the tree, to climb.