A young Ontario man took a pregnancy test and found out, via a comic strip posting on an Internet site, that he had testicular cancer.

As nutty as that sounds, the science is sound. The hormone detected by at-home pregnancy tests is the same one made by many testicular cancers. The rest of the man’s story is pure serendipity.

For laughs, the man took the pee-on-a-stick home test that he found in his medicine cabinet, left by a former girlfriend. To his shock, he was going to be a mother.

A woman friend found this hilarious, and posted a comic strip about it on the popular site Reddit, the so-called “front page of the Internet.” She posted under the name “CappnPoopdeck,” or “Capp’n” for short.

But they’re not laughing now. The comic strip resulted in a slew of viewers’ comments — and warnings. “If this is true, you should check yourself for testicular cancer. Seriously. Google it,” wrote Goxila.

The young man went to a doctor who, indeed, found a small tumor in his right testicle, according to a posting by Capp’n, who thanked fellow Redditors. She wrote that “since it was caught early, it can be treated immediately.”

The young man’s diagnosis comes as Movember kicks off in Ontario. The month-long campaign encourages men to sprout moustaches to raise funds and awareness for men’s health, specifically prostate cancer and — new this year — mental health.

The story has been widely circulating on the Internet, and the original Reddit posting has about one million hits and more than 1,500 comments.

“Capp’n” and her male friend live in Ontario, she confirmed by email to the Star, but they want to remain anonymous. The press attention on his private parts has been overwhelming.

“For the last few days, our lives have been revolving around the press demanding information about his testicle, which both of us are embarrassed and shy about talking publicly about,” she said in the email.

Here’s what the smart Redditors knew:

• Several testicular cancers produce elevated levels of beta human chorionic gonadotropin, the same hormone produced in pregnancy and detected by many of the at-home tests, explains urological oncologist Dr. Laurence Klotz of Sunnybrook Health Sciences Centre.

When testicular cancer is suspected, the patient’s blood is routinely measured for beta hCG. A blood test is more sensitive to the hormone than a urine test, he explains.

Not all types of the cancer, however, produce beta hCG. It’s present in roughly 30 to 40 per cent of cases, he estimates.

Testicular cancer tends to occur in men from post-puberty until their mid-30s, peaking in the early 20s. “It’s highly treatable and curable even when it’s spread. But the earlier the diagnosis the better,” says Klotz.

The testicle with the tumor is usually removed. The remaining testicle is most often enough for fertility. If the cancer has spread, chemotherapy and radiation may also be required.

The oncologist stresses that the best detection is self-examination, perhaps once a month in the shower, feeling the testicles for a lump or enlargement.

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So young men shouldn’t run out to buy pregnancy tests?

“Not to screen for testicular cancer,” says Klotz. “But they might have other reasons.”