Presentation
Uncomplicated standard singleton pregnancy with regular clinical and US follow-up. Physiological delivery at 38WG. At day 1, generalized hypotonia, lack of succion upon breastfeeding.
Patient Data
US standard screening until 35WG - posterior fossa and cerebellum assessment
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Normal posterior fossa scans at 26WG,32WG and 35WG. Cerebellum biometry and morphology were normal. Sylvian fissure were as according to term, normal cavum.
Day 1 CT after transfontanellar echography showing hydrocephalus
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Midline, vermis centered posterior fossa tumor bulging into the 4th ventricle, with obstructive hydrocephalus.
Tumor is heterogeneous, with cystic CSF-like densities and spontaneous hemorrhage. No internal calcification.
Round shape, no spreading through the foramen of Magendie nor the lateral foramens of Luschka.
MR at Day 1 after CT
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Midline, vermis centered posterior fossa tumor bulging into the 4th ventricle, with obstructive hydrocephalus. Hemorrhage within the occipital horns of lateral ventricles due to external ventricular drains.
Tumor is heterogeneous, with cystic CSF-like densities and spontaneous hemorrhage well seen on T2*. DWI is non-contributing due to hemorrhage. No internal calcification on CT.
Round shape, no spreading through the foramen of Magendie nor the lateral foramens of Luschka.
Peripheral enhancement.
Case Discussion
This is a case of a rapidly progressive posterior fossa tumor diagnosed on day 1 in a term newborn, which narrows down the list of possible diagnoses by a long way. Molecular genetics on pathology were typical of an atypical teratoid rhabdoid tumor.
As always in tumors, the location and age at diagnosis are key features. Posterior fossa tumors in children usually lead to possible diagnoses:
- pilocytic astrocytoma
- ependymoma
- medulloblastoma
AT/RT stands for atypical teratoid rhabdoid tumor. It mimics medulloblastoma with its round shape and midline location. However, medulloblastoma are usually found in older children around 10 years of age, with high cellularity, DWI restriction, and is rarely hemorrhagic and heterogeneous. On the other hand, AT/RT is almost exclusively found in newborns and neonates up to 2 years of age and is frequently heterogeneous. Tumor progression is rapid, as expected from embryonal malignant tumors, and the prognosis is poor. This tumor is associated with rhabdoid tumor predisposition syndrome, a genetic autosomal dominant condition which is in most cases de novo.
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