Malignant recurrence after mature Sacrococcygeal teratoma: A meta-analysis and review of the literature

Background and aims: Sacrococcygeal teratoma (SCT) is a rare extragonadal germ cell tumour mostly diagnosed during infancy and early childhood. Neonatal SCTs are mostly mature, but can also contain immature and/or malignant components. Recurrence of an SCT alters prognosis, especially when it is malignant, of which its mechanism is not yet fully understood. This study is a review and meta-analysis of the literature on malignant recurrences after an initially mature SCT. Methods: A literature search was performed to identify studies describing children with SCT and presenting specific information on histology of the initial tumour as well as the recurrence. Random effect models for mature recurrence and malignant recurrence after an initially mature SCT were employed to pool study-specific percentages in order to estimate an overall percentage and its associated 95 % confidence intervals (CI). Inverse variance method, which gives more weight to larger studies, was used to pool outcomes for the different studies. Results: A total of 22 articles, comprising 1516 patients with SCT, were included in the meta-analysis. The pooled proportions of mature and malignant recurrences after mature SCT were 3 % (95 % CI 1-4 %) and 5% (95 % CI 3-6 %), respectively. Fifty-seven (56 %) of a total of 102 recurrences after resection of an initially mature SCT were malignant, mostly yolk sac tumour (YST). Many recurrences occurred within 1-6 years, however some occurred as long as 20 years after initial diagnosis. Conclusions: A substantial number of recurrences of mature SCT present as a malignant tumour. Overlooking malignant components on initial pathological evaluation and the progression of mature SCT cells to malignant cells may play a role. Treatment of mature SCTs with resection alone requires thorough follow-up of at least 6 years. Future research is needed to determine whether SCTs with malignant microfoci should be treated or followed-up differently from mature or immature SCTs. In addition, the value of serum biomarkers in follow-up after SCT needs to be further evaluated.