Purrcat,
"The terms tumor and cancer are sometimes used interchangeably which can be misleading. A tumor is not necessarily a cancer. The word tumor simply refers to a mass. For example, a collection of fluid would meet the definition of a tumor. A cancer is a particularly threatening type of tumor. It is helpful to keep these distinctions clear when discussing a possible cancer diagnosis.
"The term cancer specifically refers to a new growth which has the ability to invade surrounding tissues, metastasize (spread to other organs) and which may eventually lead to the patient's death if untreated."
The above from a Johns Hopkins pamphlet.
Keep reading and keep learning learning. Keep a list of general questions for here, and specific to your situation questions for your care team.
As you read, you should keep seeing the statement that, "Bladder cancer, diagnosed early, is highly treatable with good outcomes."
50/50 means it could go either way. Malignant or not malignant. If it is malignant your care team will will work to eradicate the cancer or control the risk of it invading surrounding tissues.
Keep reading, stay on top of all the reports so you can make informed decisions.
Best
Jack