MRI Characteristics of Primary Tumors and Metastatic Lesions in Molecular Subgroups of Pediatric Medulloblastoma: A Single-Center Study

Multifocal (synchronous) SHH tumors at diagnosis. The multiple tumors on this axial postcontrast T1 are located in, and presumably originate within, the cerebellar cortex (A). In the second patient (B), there is 1 large fourth ventricular mass with an associated separate cortical mass posteriorly. In this case, the main tumor is lobulated and appears more like a conglomerate of multiple masses.

Metastatic group 3 tumor. In the first patient (A and B), the leptomeningeal “sugar coating” metastases demonstrate both diffusion restriction (A) and leptomeningeal enhancement on an axial postcontrast T1 image (B). In the second patient, the primary tumor appears smaller than its leptomeningeal suprasellar, avidly enhancing metastasis (C). An avidly enhancing nodular metastasis involving the cortex in the cerebellum posteriorly is also noted.

Metastatic group 4 tumors. In the first patient (A and B), the ependymal metastases seen in the anterior horns of the lateral ventricles and in the splenium of corpus callosum demonstrate diffusion restriction (B) without enhancement on contrast-enhanced T1 (arrows, B), while the leptomeningeal metastasis seen along the right temporal lobe demonstrates enhancement without appreciable diffusion restriction (arrowheads, B). In the second patient (C), the primary tumor demonstrates minimal enhancement on the contrast-enhanced T1 (arrowheads). The patient has a metastatic tumor in the suprasellar region with 2 components: One is ependymal in the infundibular recess and shows no enhancement (thin arrow), while the second is leptomeningeal and enhances strongly (thick arrow) like other metastasis in the posterior fossa, or supratentorially.