Origin and outcome of metastatic tumours to the testes: a nationwide study

Objectives: To perform a retrospective cohort analysis for metastatic tumours in the testes to explore the timing, presentation and prognosis of this particular type of metastases and the factors that influence outcome. Patients and methods: A nationwide retrospective review of pathology reports of patients with pathologically confirmed metastases to the testis between 1991 and 2021 was performed. Data were collected from the Dutch nationwide pathology databank (PALGA) and the Netherlands Cancer Registry. Log-rank testing and Kaplan–Meier analyses were used to assess overall survival (OS), and Cox proportional hazard models were used for multivariate survival analysis. Results: A total of 175 patients with a testicular metastasis were included. The median (range) age at diagnosis of testicular metastasis was 67 (3–88) years. Testicular metastases originated from a variety of primary tumours, although most frequently from the prostate (40.6%), kidney (13.7%), colon (10.3%), bladder (7.4%) and skin (5.7%). Synchronous testicular metastasis was detected in 53 cases, while 114 metachronous lesions were found after a median (interquartile range) interval of 22 (1–53) months after the original cancer diagnosis. OS after the diagnosis of a testicular metastasis was poor, with a median survival of 14.2 months (95% confidence interval 10.2–18.3). Primary tumour origin was an independent factor for survival, with worst survival for patients with primary skin, bladder and colon cancer. Conclusion: Testicular metastases are very uncommon and arise mainly from primary tumours anatomically close to the testes. Most patients develop metachronous testicular metastasis at an oligometastatic disease stage. These metastases are invariably associated with poor survival.