Do you tell a 90 year old parent that they have cancer?

My mom had a biopsy in the hospital where she was being treated for something else. She was released and then went into a rehab facility to get better to go home. Her results just came back and a family member ( medical proxy for my mom ) was told the results that she has cancer. My mom does not know yet, She has so many other health issues to deal with currently, heart disease, diabetes and kidney disease. Because of her age and history, she is not a candidate for surgery or chemotherapy. Should my mom be told she has cancer at this point in her life? The family thinks she would be devastated if she found out about the cancer. Not sure what to do. Any advise would be helpful.