Presentation
Infant presenting with a 1 week history of vomiting and ataxia.
Patient Data
Intra-axial mass lesion of the left cerebellar hemisphere, abutting the tentorium, with marked diffusion restriction of solid components, and an area of central necrosis with hemosiderin staining appreciable on the T2 images. Post-contrast sequences show mild heterogenous enhancement. A prominent intra-tumoral vessels is present, draining to the overlying dural veins. There is no appreciable surrounding vasogenic edema. Spectroscopy performed with a voxel centered on the solid portion of the tumor shows a large lactate peak, depressed NAA, inverted creatine-choline ratio and a raised myo-inositol peak.
The mass is effacing the fourth ventricle and obstructing CSF flow, with resultant hydrocephalus and periventricular edema. A right frontal approach EVD has been placed.
Mass effect results in cerebellar tonsillar descent and compression of the corticomedullary junction with associated high T2 signal changes.
Histology report (condensed)
Cellular small blue cell tumor with round-irregular, hyperchromatic, finely granular nuclei and scanty cytoplasm. Many true rosettes, no perivascular pseudorosettes. No Rosenthal fibers. No spindle cells. Occasional mitoses.
Appearances are of an embryonal tumor with differential including medulloblastoma and embryonal tumor with multilayered rosettes.
Immunohistochemistry
BCOR: positive
GPAP: majority of cells negative
syn: majority of cells negative
NeuN: patchy positive nuclear labeling
EMA: focal paranuclear dots
Comment: BCOR expression suggests, but is not definitive for, CNS tumor with BCOR internal tandem duplication.
DNA Methylation Array
Tumor classified with high confidence as a CNS tumor with BCOR internal tandem duplication.
Case Discussion
CNS tumor with BCOR internal tandem duplication is a rare and relatively new brain tumor type that has been added to the WHO classification of CNS tumors 5th edition as part of the embryonal family of tumors. It can occur both supra- and infra-tentorially, and this case demonstrates many of the typical imaging features described in the few published case series to date 1.
The main differential here includes the much more common embryonal tumor: medulloblastoma. In this age group an atypical teratoid / rhabdoid tumor (AT/RT) should also be considered. Another embryonal tumor, embryonal tumor with multilayered rosettes, shares many imaging similarities to this case but are classically supra-tentorial rather than infra-tentorial.
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