My mother (89) was diagnosed with 10 centimeter tumor on kidney. Do I tell her?

It really depends on your mother's general health and if the cyst is cancerous. Why tell her if nothing can be done and the treatment will have a negative impact on her life. A healthy 89 year old can easily have a kidney removed with no ill effects these days and it may or may not be curative. They can probably do it with a minimally invasive surgery radiation and /or chemo is a different story.

How is your mother's mental state?

If she is still the decision-maker, then her doctors have no business withholding information from her.

If not, and you are her medical proxy, then it is up to you to discuss the risks and benefits of the treatment options and act in her overall best interests, taking into account your best guess as to what she would decide for herself if she were still capable. You should explain to your mother what is happening as much and as clearly as you believe she can cope with.

And if you do have to make these very difficult decisions, comfort yourself: all you can do is your best, the only guide you have is your own judgement in the real life circumstances.

My grandmother had a cancerous kidney removed at 97 yrs and lived afterwards to be 100..Drs can do miracles..

What did her dr say about treatment? I've had several folks who have been told they had cyst on their kidneys and not to worry about them. This sounds like a large one which would have to be delt with. Some cysts are also called benign tumours and can be aspirated. Has the dr said if the tumor is malignant? What treatment did the dr recommend?