Occurrence of testicular cancer in patients operated on for cryptorchidism and inguinal hernia.

We studied the incidence of testicular cancer in 2 population-based cohorts comprising 2,918 men who underwent an operation for a cryptorchid testis and 30,199 who underwent surgery for an inguinal hernia. Complete followup during the 19-year period was achieved by record linkage to the National Swedish Cancer Registry. In the cryptorchidism cohort 4 cases of testicular cancer occurred versus 0.54 expected, yielding a relative risk of 7.4 (95% confidence interval 2.0 to 19.0). Of these patients 3 had undergone a bilateral operation due to intra-abdominal testes. There was no evidence of an association between inguinal hernia and risk of testicular cancer (relative risk = 1.1, 95% confidence interval 0.4 to 2.2). The validity of our data was further supported by relative risk estimates close to unity in a comparison group of appendectomy patients. We conclude that patients with a cryptorchid testis experience a substantially increased relative risk of testicular cancer. However, the low absolute risk, 4 cases during 25,360 person-years of observation, does not appear to justify special surveillance after an operation for an undescended testis.