Posterior fossa immature teratoma in an infant with trisomy 21: A case report and review of the literature.

BACKGROUND: Intracranial teratoma associated with Down syndrome is rare. With only three previously reported cases, our case is the first one presenting an immature component.

CASE DESCRIPTION: A 2-month-old boy with trisomy 21 presented with lethargy and head enlargement. A magnetic resonance imaging (MRI) study showed an obstructive hydrocephalus with 0.5 cm posterior fossa tumor compressing the cerebellum. The tumor revealed a mixed intensity on T1- and T2-weighted MRI images and was surrounded by peritumoral cysts. It was heterogeneously enhancing and showed multinodular mass. The tumor was gross totally removed via suboccipital craniotomy and histologically diagnosed as immature teratoma. Four cycles of chemotherapy consisting of cisplatin and etoposide followed the surgery. The radiotherapy was withheld due to infancy. Recurrent lesions in the tumor bed were noted 10 months later. They were removed in the second surgery and histologically identified as mature teratoma.

CONCLUSION: Maturation of immature teratoma may be a result of natural conversion of multipotent embryonal cells into mature tissues and following chemotherapy.