Testicular cancer is the most common form of cancer among young men, and it often produces no symptoms. Researchers have now identified a big one: Men who are infertile and have abnormal sperm counts are more than 20 times as likely to have testicular cancer as other men. A team of researchers from NewYork-Presbyterian Hospital/Weill Cornell Medical Center reviewed the records of more than 3,800 men with infertility or abnormal counts and found that 10 had testicular tumors.

Eight of the men had no other risk factors for the disease, according to the study, which appeared in the November issue of the Journal of Urology. Two had a history of at least one undescended testicle, known to be a risk factor for testicular cancer. Even excluding those two men, the risk was still more than 18 times higher than among other men. All of the tumors were the same kind, a type known as a seminoma, which usually makes up about half of testicular cancers.

Those figures mean that the odds of finding testicular cancer in an infertile man are about 1 in 500, the study says. That sounds small, but the odds are great enough that men who have an abnormal sperm count or are infertile should be referred to a urologist for examination and possible ultrasound screening, says lead author Marc Goldstein, surgeon in chief of male reproductive medicine and surgery at the medical center. (As a comparison, regular mammograms are recommended for women over 40 though the odds of finding breast cancer are just 1 in 1,438.) The recommendation for referral holds true even if the couple's infertility can be solved using IVF or other methods, says Goldstein. In an editorial accompanying the study, Raymond Costabile, a urologist at the University of Virginia, recommends these men also perform regular testicular self-examinations.

Researchers still don't know why male infertility is associated with testicular cancer but suspect some kind of underlying genetic predisposition to both abnormal sperm characteristics and testicular tumors.