Background: The aim of this study was to determine the prevalence of testicular carcinoma in situ (CIS) in patients with a malignant extragonadal germ-cell tumour (EGGCT) and the incidence of metachronous invasive testicular cancer (TC) in relation to the pretreatment demonstration of CIS.
Patients and methods: Sixty-eight patients with EGGCT (53 retroperitoneal, 15 mediastinal) had pre-chemotherapy histological assessment of one (13) or both (55) testicle(s). A total of 123 testicles were examined for the presence of CIS.
Results: Testicular CIS was found in 21 patients (31%) (18 retroperitoneal EGGCT, three mediastinal EGGCT). Two patients had bilateral CIS. Five patients, four of them with proven pretreatment CIS, developed a metachronous TC. The 10-year invasive-free TC survival rate for all 68 patients was 88%, but only 65% for those with proven pretreatment CIS. The overall 10-year survival rate for all patients was 82%. CIS was demonstrated in seven of 48 trans-scrotal core biopsies, in 10 of 56 trans-scrotal surgical biopsies and in five of 11 orchiectomy specimens.
Conclusions: Approximately one-third of patients with EGGCT present with testicular CIS, predominantly those with a retroperitoneal tumour. These patients have a considerable risk of metachronous TC development in spite of chemotherapy. The pretreatment demonstration of testicular CIS in patients with EGGCT gives the possibility of individualised counselling and safe follow-up, and is therefore highly recommended. The data are in agreement with a multi-site development of malignant germ-cell tumours, but do not exclude the possibility that the retroperitoneal EGGCTs in particular represent metastases from a burned-out TC.