What Causes Testicular Cancer? - The Author's hypothesis is Ochratoxin A - This is a transcript of a presentation made at a medical conference. It is not hard to follow, and is more pursuasive than most discussions in this area.
There are a number of articles on the Internet discussing the discovery of a testicular cancer gene in 2000. Unfortunately, it was later shown that this finding was caused by a problem with the data set in the analysis. When that error was corrected, the evidence for the testicular cancer gene disappeared.