Presentation
Upper limb numbness.
Patient Data
Left cerebellar mass with surrounding vasogenic edema with mild mass effect of the fourth ventricle.
Intra axial left cerebellar mass is T1 hypointense, T2 hyperintense with central foci of cystic change and demonstrates homogeneous enhancement. Moderate amount of surrounding FLAIR hyperintensity but no significant mass-effect with pain in fourth ventricle and no hydrocephalus. The enhancing components demonstrate homogeneous diffusion restriction (ADC 560).
Suggestion of a tiny focus of leptomeningeal enhancement of the adjacent posterior vermis. No susceptibility artefact on SWI. No other mass lesion is identified.
Minimally increased CBV within the center of the mass.
MICROSCOPIC DESCRIPTION: All the sections show a densely cellular malignant tumor, adjacent to cerebellar cortex. It has a nodular architecture with scattered pale islands. The tumor cells have high N/C ratio with elongated and hyperchromatic nuclei, nuclear molding, focal prominent nucleoli and scanty cytoplasm. Within the nodules, the tumor cells are more widely spaced and with more fibrillary matrix. Scattered mitoses are seen, along with apoptotic debris. The features are those of desmoplastic/nodular medulloblastoma. The reticulin stain shows fibers in-between the nodules but absent in the pale islands. The tumor cells are focally synaptophysin and chromogranin positive. The topoisomerase index is about 20%. INI1 and NeuN are negative.
B-catenin is negative. GAB1 and YAP1 are focally positive. p53 is negative in most of the tumor cells.
DIAGNOSIS: Desmoplastic/nodular medulloblastoma, SSH-activated and TP53-wildtype (WHO Grade IV).
Case Discussion
The desmoplastic/nodular SSH medulloblastoma, which this is, tend to occur in the lateral parts of the cerebellar hemispheres and more common in young children (<4 years) and adults (>16 years) with an equal M:F.
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