Testicular cancer has a few well-established risk factors, including undescended testes and a history of contralateral germ cell tumor. Family history has also been suggested as a possible risk factor, even though no convincing data clearly identify a prevalence of familial testicular cancer in populations with testicular cancer. Dieckmann and Pichlmeier conducted a three-part investigation, including a prospective study, a retrospective analysis of a large patient population, and a review of the literature, to identify relative risk estimates and assess the prevalence of familial testicular cancer.

A total of 1,692 patients with testicular germ cell tumors were given a questionnaire to evaluate their family history of testicular cancer. In a retrospective analysis, 518 patients with testicular cancer were asked if they had any relatives who had been diagnosed previously with testicular cancer. Another group of 531 patients were used as age-matched control subjects. The literature review included only reports that addressed the prevalence of familial testicular cancer and included at least 200 patients.

In the patients from the prospective study, 28 reported that a family member had a germ cell testicular tumor, corresponding to an overall prevalence of familial testicular cancer of 1.7 percent. In the retrospective analysis, 13 of the 518 patients with testicular cancer had a family history of the disease, corresponding to an overall prevalence of 2.5 percent. Only three of the 531 control subjects reported a family history of testicular cancer, for a prevalence of 0.56 percent. The literature review identified 10 studies that examined the prevalence of familial testicular cancer in populations of more than 200 patients. The reported prevalence of familial testicular cancer ranged from 1.0 to 2.8 percent, with a mean prevalence of 1.35 percent.

The authors concluded that genetic predisposition is a definite independent risk factor for testicular germ cell tumors. Having a first-degree family history of testicular cancer confers a three- to 10-fold increased relative risk. The goal for future research is to identify this inherited predisposing defect for familial testicular cancer on a molecular genetic level.