Fig 6. 15-month-old boy with atypical teratoid/rhabdoid tumor (AT/RT) (Patient 32).

A, Axial T2-weighted image at level of middle cerebellar peduncles shows a large heterogeneous mass of predominantly low to isointense signal intensity that is almost completely effacing the fourth ventricle. The temporal horns of the lateral ventricles are dilated with signs of transependymal CSF flow (arrowheads), consistent with obstructive hydrocephalus.

B, Contrast-enhanced T1-weighted image with fat saturation corresponding to A shows heterogeneous enhancement of the tumor. A nonenhancing cystic area (arrow) is also seen that is likely to correspond to trapped CSF adjacent to the tumor.

C, ADC at a similar level as A and B reveals that the lesion is of lower diffusion than the normal brain parenchyma. The lateral cystic area shows diffusion properties of CSF.

D, Photomicrograph of AT/RT shows high cellularity and cytoplasmic pink densities (arrows) (hematoxylin-eosin stain, 40x).