How can I find out if I have a defective tumor suppressor gene?

Genetic testing. However, this is a very broad question. There are hundreds of tumor suppressor genes, and they are not randomly tested. You need to know which specific tumor you are interested in, and then the specific test can be requested or performed, if appropriate. You state "adrenal tumor", but I am not sure if that is adrenal cortical carcinoma or not.