A Rare Case of Bone Marrow Infiltration of Disseminated Medulloblastoma in a Young Adult.

Medulloblastoma is the most common primary CNS malignant neoplasm in the paediatric age group, accounting for 12 to 20 % of all childhood malignancies, but medulloblastoma in an adult is rare. We report a case of a 31-year-old male who presented with an inability to walk and episodic vomiting. MRI of the brain revealed a midline lesion involving the vermis and cerebellar hemispheres. Excision and immunohistochemistry confirmed the diagnosis of medulloblastoma, desmoplastic/nodular. After 10 months, he had a recurrence of the tumour and a redo surgery was attempted, followed by 6 # cycles of chemotherapy. The patient was lost to follow-up; 3 years later, PET-CT showed multiple metastases to the lung and cervical lymph node along with bicytopenia. The bone marrow study revealed interstitial infiltration by small round blue cells. Immunohistochemistry showed these cells were positive for synaptophysin, supporting a diagnosis of medulloblastoma metastasis to the bone marrow.