Prevalence of contralateral testicular intraepithelial neoplasia in patients with testicular germ cell neoplasms.

PURPOSE Testicular intraepithelial neoplasia ([TIN], so-called carcinoma in situ of the testis) is hypothesized to be the precursor of testicular germ cell neoplasms. According to previous studies, it can be detected by testicular biopsy. Since patients with a unilateral testicular tumor are at high risk of a second testicular tumor, it seemed feasible to examine the prevalence of contralateral TIN in patients with testicular germ cell cancer and correlate it with the known prevalence of bilateral testicular tumors. The aim was to provide more evidence for the role of TIN as the preinvasive stage of testicular cancer. PATIENTS AND METHODS Nineteen hundred fifty-four consecutive patients with a unilateral testicular germ cell tumor underwent contralateral biopsy. All specimens were examined immunohistologically. RESULTS TIN was observed in 4.9% (95% confidence interval [CI], 3.95% to 5.91%). Testicular atrophy and a history of undescended testis were more frequently observed in patients with contralateral TIN, but only atrophy was shown to be independently associated by multivariate analysis. Patients with testicular atrophy have a 4.3-fold increased risk of having contralateral TIN. Sixty-four percent of TIN cases were found in normal testes. Patients with TIN were significantly younger than those without (P < .0017). Three patients developed a second testicular tumor despite a negative biopsy for TIN. CONCLUSION The prevalence of contralateral TIN corresponds well to the known prevalence of bilateral testicular tumors. Testicular atrophy is a strong indicator for the presence of TIN, but approximately 60% of TIN cases occur without atrophy. The present data are in accordance with the theory that TIN is an early step in the histogenesis of testicular germ cell neoplasms.