Case 028

History/Physical

History/Physical:

10-year-old right-handed male.

Ataxia and headache for two weeks.

The left cerebellar masses (*) are slightly hypointense on T1.

The masses (*) enhance avidly. There is tonsilar herniation (arrows).

The mass (*) is intra-axial.

The masses appear mostly solid and enhance avidly (*).

There is mass effect on the 4th ventricles and basilar artery (arrows).

Vasogenic edema (arrow) has higher signal on T2 than the mass (*).

Diagnosis: Medulloblastoma, classic (non-WNT, non-SHH)

Small blue-cell tumour with some nodule formation (*).

Primitive cells with nuclear molding, speckled chromatin and mitotic activity.

Tumour cells form enfilades and rosettes.

Nodules demonstrate neuronal differentiation by synaptophysin expression.

Scattered tumour cells display glial differentiation by glial fibrillary acidic protein expression.

Light cytoplasmic expression of beta-catenin (no nuclear expression)

Abundant proliferation as demonstrated by Ki-67 labeling. Note higher proliferative index between nodules.
Molecular profiling favoured classification as group 4.