Ben Stiller has revealed his battle with "aggressive" cancer and it's taught us a powerful lesson.

Veteran Hollywood actor Ben Stiller revealed on Tuesday that he survived a battle against “mid-range aggressive” prostate cancer in 2014.

Sharing the news in a blog post titled “The Prostate Cancer Test That Saved My Life” on Medium, the Zoolander star began, “My urologist segued from talking about how inconvenient it was picking his daughter up at school that morning to dropping a cancer diagnosis on me without missing a beat. Two weeks earlier, I didn’t even have an urologist.”

Ben Stiller in his iconic Zoolander role. Source: Ben Stiller / Facebook.

Now cancer free for two years, the 50-year-old said he decided to share the news in a bid not just to encourage more men to be tested early for prostate cancer, but also to defend the controversial PSA (Prostate Specific Antigen) test, which Stiller says saved his life.

"The bottom line for me: I was lucky enough to have a doctor who gave me what they call a “baseline” PSA test when I was about 46. I have no history of prostate cancer in my family and I am not in the high-risk group, being neither — to the best of my knowledge — of African or Scandinavian ancestry. I had no symptoms," Stiller explained.

"What I had — and I’m healthy today because of it — was a thoughtful internist who felt like I was around the age to start checking my PSA level, and discussed it with me."

According to Stiller, there is controversy around the "painless blood test" because results are dependent on how doctors interpret the data and the recommendations that follow.

Ben Stiller in Anchorman. Source: Ben Stiller / Facebook.

"Doctors can send patients for further tests like the MRI and the more invasive biopsy, when not needed," the father of two explained, adding, "In some cases, men with this type of cancer get “over-treatment” like radiation or surgery, resulting in side effects such as impotence or incontinence. Obviously this is not good; however it’s all in the purview of the doctor treating the patient."

But without the PSA test, the Walter Mitty star continued, cancers like his, would not have been detected at all.

Ben Stiller with Zoolander 2 castmates, Will Ferrell, Penelope Cruz and Owen Wilson. Source: Ben Stiller / Facebook.

Speaking to Howard Stern following the tell-all blog post, Stiller explained, “It came out of the blue for me. I had no idea.”

“At first, I didn’t know what was going to happen. I was scared. The one thing that it does, it just stops everything in your life when you get diagnosed with cancer, because you can’t plan for a movie, because you don’t know what’s going to happen.”

Within three months of detection, though, Stiller had undergone surgery and was deemed cancer free.

According to the Cancer Council, over 18,000 Australian males are likely to be diagnosed with prostate cancer in 2016.

Further information about prostate cancer can be found here.