Malignant transformation and tumour recurrence in sacrococcygeal teratoma: a global, retrospective cohort study.

Introduction: Sacrococcygeal teratoma (SCT) is a rare congenital tumour. The risk of malignancy and recurrence are not well defined. Previous studies are small and report differing conclusions about the timing of surgery and the duration of follow-up. We studied the risk of malignant transformation and SCT recurrence after surgery to address these gaps.

Methods: This was a global retrospective cohort study. Data of consecutive SCT patients was obtained from 145 institutes in 62 countries. Malignant transformation, defined as malignancy at initial resection, malignant recurrence or death due to malignancy, and its risk factors were analysed.

Results: Of the 3612 included patients, 3407 entered analysis. Risk of malignant transformation of the initial tumour, was 3.3%, 5.1%, 10.1%, and 32.9% at age three months, six months, one year, and two years, respectively. After six years, the censored risk of malignancy (64%) did not further increase. Recurrent SCT was diagnosed in 349 (10·2%) children with 126 (36·1%) malignant recurrences. Risk factors for recurrence were Altman type II (odds ratio (OR): 1·6, 95% confidence interval (CI): 1·2-2·3), Altman type III (OR: 1·6, 95% CI: 1·2-2·3), initial immature histology (OR: 1·9, 95% CI: 1·4-2·6), and initial malignant histology (OR: 4·0, 95% CI: 2·9-5·4).

Conclusion: The risk of malignancy at initial resection in SCT increases with age reaching a plateau at six years of age. Recurrence after resection occurred in 10% of patients and 36% of these were malignant at that time. Altman type II or type III, and immature or malignant histology were associated with recurrence.

Level of evidence: level III.