OBJECTIVE: To evaluate if optimised and standardised diagnostic procedures would improve detection of germ cell neoplasia in situ (GCNIS) in the contralateral testis of patients with testicular germ cell tumour (TGCT), and decrease the rate of metachronous tumours, which in the nationwide Danish study was estimated as 1.9%.

PATIENTS AND METHODS: This is a retrospective analysis of the outcome in 655 patients with TGCT who underwent contralateral biopsies (1996 - 2007), in comparison to 459 non-biopsied TGCT controls (1984 -1988). The biopsies were performed using a standardised procedure with immunohistochemical GCNIS markers and assessed by experienced evaluators. Initial histopathology reports were reviewed, and pathology and survival data were retrieved from national Danish registers. In 604/608 patients diagnosed as GCNIS-negative (4 were lost to follow-up), the cumulative incidence of metachronous TGCT was estimated in a competing risk setting by the Gray method. All cases of metachronous TGCT were re-examined by immunohistochemistry.

RESULTS: GCNIS was found in 47/655 biopsied patients (7.2%, 95% CI 5.4-9.5%). During the follow-up period (median 17.3 years) five of the 604 GCNIS-negative patients developed a TGCT. In 1/5 false-negative biopsies GCNIS was found upon revision and 2/5 biopsies were too small. The estimated cumulative incidence rate of the second tumour after 20 years of follow-up was 0.95% (95%CI 0.10%-1.8%) compared with 2.9% (1.3%-4.4%) among the non-biopsied TGCT patients (p=0.012). The estimates should be taken with caution due to small numbers of men with metachronous TGCT.

CONCLUSIONS: Optimised diagnostic procedures improved the detection rate of GCNIS in patients with TGCT and minimized their risk of developing metachronous bilateral cancer. Urologists must be aware of the importance of the surgical procedure and an adequate biopsy size. Performing contralateral biopsies is beneficial for the patients' care and should be offered as a part of the management.