Presentation
Headache
Patient Data
Well-defined rounded hyperdense lesion is seen at the right aspect of the posterior fossa with surrounding hypodense rim of cerebellar edema. It exerts mass effect compressing the cerebellum and 4th ventricle with moderate supratentorial hydrocephalus and crowding at the foramen magnum.
The lesion shows heterogenous signal on different sequences with central areas of high T1 and dark T2 signal and significant blooming on SWI (denoting hemorrhagic component). It shows areas of diffusion restriction and mild heterogenous post contrast enhancement.
Case Discussion
The patient underwent surgical excision of the lesion.
Histology:
Microscopy:
Sections examined revealed multiple cellular tumor tissue fragments, displayed as clusters, aggregates, and sheets of intermediate sized round to ovoid cells exhibiting enlarged irregular darkly stained nuclei with focal molding and scanty with intervening fibrous stromal bands with fair vascularity. Focal nodular pattern with compartmentalization and central pale zones were observed. Focal vague rossetting was seen. Islands of tumoral necrosis were noted.
Diagnosis:
Undifferentiated round cell malignancy suggestive of medulloblastoma, desmoplastic/nodular variant (WHO grade IV).
Immunophenotyping and molecular testing were not done. Although molecular testing was not done, the lateral location of the lesion with desmoplastic/nodular pattern on histology suggests that it's likely of the sonic hedgehog (SHH) molecular subgroup.
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