If you've been near social media or on the Internet, you may be aware of the buzz over posts claiming a teenage boy took a home pregnancy test as a joke, received a positive result, and wound up being diagnosed with testicular cancer.

CNN interviewed a girl who identified herself as a friend of the 17-year-old, but was not able to independently confirm the posts.

However, it's true home pregnancy tests can detect some types of testicular cancer in men, experts say - but the tests would not be useful as a screening tool.

According to the American Cancer Society, pregnancy tests work by detecting a hormone called Beta-HCG (human chorionic gonadotropin). Beta-HCG is produced by the cells of a woman's placenta during pregnancy, but is also excreted by some tumors "including some, but not all, testicular cancers," the cancer society says.

"At the time of diagnosis, only a small minority of men with testicular cancer have HCG levels high enough to be detected by a home urine pregnancy test," says Dr. Ted Gansler, director of medical content for the American Cancer Society, in a statement. "More sensitive blood tests for HCG with a lower cutoff level could detect a somewhat higher percentage, but several non-cancerous conditions can cause false positive results.

"Current evidence does not indicate that screening the general population of men with a urine test for HCG (or with urine or blood tests for any other tumor marker) can find testicular cancer early enough to reduce testicular cancer death rates," Gansler says.

Gansler told CNN in an e-mail that "much less often, some other cancers might cause a positive pregnancy test." Medical journals have documented that both men and women patients with pancreas, lung, stomach or other cancers may have HCG levels high enough to cause a positive pregnancy test result, he says.

A lump on the testicle is the first sign of cancer, according to the cancer society, and men should see a doctor right away if one is found.

But even regular self-exams aren't recommended by the ACS because they have not been studied enough to show they reduce the death rate from testicular cancer. "Without that evidence, the American Cancer Society cannot make a recommendation on regular testicular self-exams for all men," the organization said. "But we do think men should decide for themselves whether or not to do regular exams."