Do retroperitoneal extragonadal germ cell tumours exist?

INTRODUCTION: Extragonadal germ cell tumours (GCTs) have been described arising in midline structures. Although primary retroperitoneal extragonadal GCTs (RPGCTs) comprise 30% to 40% of these, their existence as a genuine disease has been questioned. Our study evaluated clinicopathological findings to examine this question in RPGCT patients at our centre.
METHODS: Data from 414 men between 1980 and 2014 treated at London Health Sciences Centre with chemotherapy for testicular GCTs were reviewed retrospectively. Primary RPGCT was defined as pathologically diagnosed GCT with no evidence of GCT in the testes by physical exam or ultrasound. Patients thought to have primary RPGCT at the time of initial diagnosis were identified from an electronic database and data were extracted.
RESULTS: In total, 18 men with a diagnosis of metastatic RPGCT were identified. Four were excluded due to ultrasound reports that were incomplete or suggested malignancy. The remaining 14 patients had negative or non-specific ultrasounds, and all received platinum-based combination chemotherapy. Ten patients (71%) underwent post-chemotherapy RP lymph node dissections; of those 8 (57%) who underwent orchiectomy, none had corresponding pathologically normal testicular tissue.
CONCLUSION: RPGCT patients present with more advanced disease stage. Our study sample size is limited, but the findings are consistent with existing literature suggesting that primary RPGCTs may not exist as a unique disease, but instead may represent metastatic disease from a clinically occult testicular primary. By corollary, viable malignant germ cells may be present in testes of patients with presumed primary RPGCT, and may persist as a site of residual malignant disease after chemotherapy.