Blood tests are sometimes helpful in diagnosing testicular tumors. Many testicular cancers secrete high levels of certain proteins, such as alpha-fetoprotein, or AFP, and human chorionic gonadotropin, or HCG. Testicular tumors can also increase the levels of some enzymes, such as lactate dehydrogenase, or LDH. These proteins are known as tumor markers because the presence of these proteins in the blood suggests that a testicular cancer is present. However, it's important to remember that these proteins can also result from conditions other than cancer.
The proteins that are present will vary depending on the type of testicular cancer. Nonseminomas often raise AFP and HCG levels. Seminomas occasionally raise HCG levels, but do not raise the level of AFP. A high LDH can sometimes indicate widespread cancer, but this is not always the case.