Somatic malignant transformation in a sacrococcygeal teratoma in a child and the use of F18FDG PET imaging.

A 6-year-old female presented with a subcutaneous sacral mass. Biopsy revealed an adenocarcinoma most likely arising from a sacrococcygeal teratoma (SCT). CT imaging revealed a massive tumour consistent with SCT. F(18)FDG Positron Emission Tomography (PET) scan confirmed marked metabolic activity in the tumour mass and regional lymph node involvement. After chemotherapy repeat CT and PET studies revealed a poor response but no evidence of peritoneal or distant metastases. Radical abdomino-pelvic and gluteal surgery was performed with removal of the entire tumour confirmed as a moderately differentiated adenocarcinoma arising in an immature teratoma. Follow up imaging including PET scanning 5 months after her surgery revealed widespread peritoneal, hepatic and pulmonary metastases. Somatic malignant transformation of an SCT in a child of this age has not been previously reported.