A positive pregnancy test - taken by a man as a gag - led him to find out he had testicular cancer.
The man, whose name hasn't been publicly released, found an unused pregnancy test that had been left in his home by his ex-girlfriend. As a joke he decided to pee on the stick and was shocked when he received a positive result.
He posted a comic about the result on Reddit to share the strange story. But savvy users urged him to see a doctor.
"If this is true story, go see a doctor. Pregnancy test detects increased HcG level. In male around age of 30s, increased level of HcG could indicate Embryonal Carcinoma or choriocarcinoma," one reader commented.
"If this is true, you should check yourself for testicular cancer. Seriously. Google it," another wrote.
Pregnancy tests check for the presence of a hormone called beta human chorionic gonadotropin, Medical Daily reported. In pregnant women the hormone appears in the urine and blood as a result of the growing placenta.
But other conditions can produce the hormone - like testicular cancer.
The man visited his local GP where tests revealed he had a small testicular tumour which was caught early enough, although he may still have to have his testicle removed.