Histopathological and molecular features of late relapses in non-seminomas

OBJECTIVE: To describe the histopathological types of late relapses of germ cell tumours and to search for molecular markers associated with chemotherapy resistance. PATIENTS AND METHODS: Samples from 14 patients with late relapse from a non-seminoma were analysed. • Archival tumour tissue was gathered at intial diagnosis (n = 9) and at relapse (n = 9), mostly after previous treatment with chemotherapy. • In addition to routine histopathology, tumours were analysed for microsatellite instability and screened for mutations in the KRAS and BRAF genes. RESULTS: Relapse occurred after 76.5 months (median, range: 24-209 months). • The histology in relapse was pure yolk sac tumour in four of the nine patients analysed. • Three had a non-germ cell malignancy, one was a mixed non-seminoma and one was a pure mature teratoma. • One sample with non-germ cell malignancy originated from a yolk sac tumour without any evidence of teratoma. • In four of 12 evaluable patients, high-level microsatellite instability was observed. • All patients were KRAS wild-type but four showed a BRAF mutation at V600E. CONCLUSIONS: Many late relapses of germ cell tumours show pure yolk sac histology. • Non-germ cell malignancies do not necessarily develop from teratoma but can also arise from yolk sac histology. • The biology underlying chemotherapy resistance in late relapse could be related to a high incidence of microsatellite instability and BRAF mutation V600E, which were found in half of the patients.

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