Ben Stiller has revealed he was diagnosed with an 'aggressive' form of cancer two years ago - and secretly had surgery to remove his prostate.



The actor, 50, opened up about his battle with the disease for the first time in an interview on Tuesday's Howard Stern Show.



He said his doctors diagnosed him with 'immediately aggressive' prostrate cancer in June 2014 and two months later, he underwent surgery.



By September that year, he was told he was cancer-free.



Now, he is urging men to speak to their doctors about being tested at an earlier age.



'It came out of the blue for me,' Stiller said. 'I had no idea.' 



His tumor had been growing for five years, he said, and had he not had a PSA (prostate-specific antigen) test done, he wouldn't have realized he had one.



On Tuesday morning, he also took to Twitter to share a blog post opening up about his ordeal and again, urging people to get tested.



'So, I had cancer a couple of years ago and I wanted to talk about it. And the test that saved my life,' he wrote alongside a link to his post on medium.



Stiller described being told about his cancer as like a scene out of a movie.



He said his urologist's voice 'literally faded out like every movie or TV show about a guy being told he had cancer… a classic Walter White moment, except I was me, and no one was filming anything at all.'



While processing the news, he said he started Googling men who had faced prostate cancer and survived: John Kerry, Jon Torre, Mandy Matinkin, Robert DeNiro.



'As I learned more about my disease (one of the key learnings is not to Google 'people who died of prostate cancer' immediately after being diagnosed with prostate cancer), I was able to wrap my head around the fact that I was incredibly fortunate,' he wrote.



'Fortunate because my cancer was detected early enough to treat. And also because my internist gave me a test he didn't have to.



'I got diagnosed with prostate cancer Friday, June 13th, 2014. On September 17th of that year I got a test back telling me I was cancer free. The three months in between were a crazy roller coaster ride with which about 180,000 men a year in America can identify.



'Taking the PSA test saved my life. Literally. That’s why I am writing this now.'



He added: 'If [his doctor] had waited, as the American Cancer Society recommends, until I was 50, I would not have known I had a growing tumor until two years after I got treated.



'If he had followed the US Preventive Services Task Force guidelines, I would have never gotten tested at all, and not have known I had cancer until it was way too late to treat successfully.'



Stiller had his PSA test when he was 46, four years before the American Cancer Society recommends. Many experts say a PSA can do as much harm as good.



He addressed the controversies surrounding the test, saying: 'It is a simple, painless blood test. It is not dangerous in itself in any way.



'If the PSA (Prostate Specific Antigen) value is elevated in the blood, or levels rise sharply over time, it could indicate the presence of prostate cancer. It is definitely not foolproof.'