What was supposed to be a funny post about a guy friend who tried out a pregnancy test for laughs might have helped catch a form of cancer early in its tracks.

Five days ago, a woman going by the Reddit handle “CappnPoopdeck” posted a comic in which she laughed at a friend who decided to pee on a pregnancy test stick that had been left in his bathroom medicine cabinet by an ex-girlfriend. To his surprise, the test came back positive.

“I’m pregnant,” the man’s caricature marvelled.

But within hours, readers started leaving comments that the friend might want to get checked for testicular cancer.

“If this is true, you should check yourself for testicular cancer. Seriously. Google it,” wrote the first commenter to raise the alarm, “goxilo.”

The reason for their concern is that pregnancy tests look for levels of human chorionic gonadotropin, or hCG. A few of the commenters pointed “CappnPoopdeck” to a Wikipedia entry that noted that while hCG is a hormone that’s released by a developing placenta, a form of it is also secreted by some cancer tumours, including those of testicular cancer.

Others agreed and urged the man to get tested.

"You may have testicular cancer! Get to an oncologist, tell them you took a pregnancy test and it came out positive," a Redditor wrote.

“Go check yourself, reasons for human corionic gonadotropin in male's urine is ussualy testicular cancer (sic),” wrote another.

“CappnPoopdeck” responded quickly to the responses.

“Whoa.. just saw all the cancer comments... It was my friend that did the test, I just made the comic for him.. but I am letting him know to test himself for cancer immediately. Thank you for letting me know guys, we may have dodged a bullet here!” she wrote.

The man went to a see a doctor on Monday. On Tuesday, “CappnPoopdeck” posted a new comic that revealed her friend’s doctor had in fact found a small tumour in the man’s right testicle.

“Since it was caught early, it can be treated immediately,” she wrote.

“So both of us want to say thank you, and in all seriousness, if you are male check yourself for testicular cancer regularly,” she added.

The treatment for testicular cancer is usually removal of the affected testicle. The good news is that the cancer has a very high survival rate.

According to the Canadian Cancer Society, testicular cancer has a 95 per cent five-year survival rate.

The agency notes it generally affects younger men, between the ages of 15 and 49 and is the most common cancer in young males between 15 and 29.

Around 940 men will be diagnosed with testicular cancer in Canada in 2012, but because of the high cure rate, only 36 men will die of testicular cancer in 2012.

In most cases, only one testicle is affected. Even after the removal of one testicle, most men go on to have normal sex lives and have no problems with fertility.

“CappnPoopdeck” has since expressed irritation with the amount of media attention the story has gotten, as well as irritation with those who have suggested the whole story was made up.

But for most readers, it’s a great example of the power of social media in raising awareness of what could have been a serious illness.