Ben Stiller Battled Prostate Cancer

Ben Stiller is revealing his prostate cancer diagnosis, and delivering an important message for men -- don't avoid your doctor's finger ... 'cause it could save your life.

Ben went on "The Howard Stern Show" Tuesday ... speaking publicly for the first time about discovering the prostate cancer 2 years ago. He says he beat it after undergoing surgery.

But Ben really wanted to get into the big debate about when to get tested and what kind of test to take. He shared his experience -- in detail -- and believes it could help you.

Check out the clip ... important stuff, but entertaining too.