Four recent diagnoses of testicular cancer in the Bundesliga have grabbed attention and shocked many.

While Timo Baumgartl (Union Berlin) and Marco Richter (Hertha Berlin) have recovered and are back on the pitch, Sebastien Haller (Borussia Dortmund) and Jean-Paul Boetius (Hertha Berlin) are still on the road to recovery — Haller has since had to undergo a second operation. Is this cluster of testicular cancer cases a coincidence? Or do the diagnoses have some connection to professional sport?

"This is an accumulation that may be coincidental," sports physician Wilhelm Bloch told DW.

Bloch is a sports medicine specialist who has been researching cancer and sport for many years and works at the German Sport University Cologne.

"Most of the scientific studies show that there is no accumulation," Bloch said, adding that testicular cancer is a disease that most often strikes men at a young age.

Cycling studies

There are about 4,000 testicular cancer cases in Germany every year, with the disease most common among adults 20-40 years of age.

"At the moment there is no scientific evidence that the illness is more common in young athletes," Bloch said.

There are other factors involved, such as the fact that young men over 6 feet (1.82 meters) tall are more likely to be affected by testicular cancer, "which could be related to their growth and muscular system," Bloch said.

In addition, hormones, externally provided or the man's own, also play a role with this disease. According to Bloch though, a specific cause of testicular cancer has not yet been discovered.

Cycling has been proactive in investigating a possible connection between the disease and the sport.

"Sitting on the saddle actually puts permanent pressure on the testicles, which can lead to microinjuries," Bloch said. "But, even in cycling, it has not been possible to determine an accumulation."

No possibility of prevention

Bloch believes that other influential factors could become more of a focus.

"The body temperature, somewhat," Bloch said. "Athletes often reach temperature ranges that most people don't."

Furthermore, Bloch said, intense exercises alters hormone balance, and genetic factors may also play a role in the disease's developing in young people.

Bloch said scientists had yet to find any methods of preventing the disease, but the doctor has a positive message for people currently suffering from testicular cancer.

"Testicular tumors are so-called germ cell tumors," Bloch said. "These are easily treatable — especially if diagnosed early. In many cases, the affected athlete can return to sport quite quickly."

Bundesliga players unsettled

Even if, from a scientific perspective, there is currently no connection between testicular tumors and playing sport, the cases in the Bundesliga have left players unsettled.

"Players are worried at the moment and are sensitive to the issue, which is why many are now getting themselves checked out," Karl-Heinrich Dittmar, Bayer Leverkusen's team doctor, told DW. "It's not such a rare tumor disease in young men."

Players do undergo regular medical examinations, but those mandated by the DFL, which operates the Bundesliga, do not routinely include urological checks.

"At Leverkusen, we do the usual MRI, where the pelvis and the thighs are shown. The testicles can also be seen on this image and you can see already here if something is up. There are also tumor markers in the blood, which we can determine with every blood test," Dittmar said.

"What we do at our screenings is sufficient," he said, "because the blood parameters we determine are very sensitive."

Since 2002, when Dittmar started work at Leverkusen, the club have not had a case of testicular cancer. He believes that the current number of cases is too low to draw a connection with football.

"It's more of a coincidence," Dittmar said. "But that doesn't mean we won't continue to be very vigilant in the future."

This article was updated from its original version to include Sebastien Haller's second operation.

This article was originally written in German.