Primary intracranial sarcomas of mesenchymal origin are rare and challenging to diagnose. One such tumor has a DICER1 mutation, which is primarily seen in pediatric EBV positive patients as the virus allows for proliferation of the neoplasm. Radiographically, these tumors may be a solid or cystic mass with or without hemorrhage, and possible leptomeningeal attachment. Limited cases of such tumors exist so pathophysiology remains unclear while the gold standard diagnosis is pathology.

The patient is a 53-year-old female with history of post traumatic headaches and hypertension, with initial presentation in January 2023 with vertigo. MRI revealed leptomeningeal enhancement in the medial right frontal lobe. Surveillance MRI in May 2023 showed increased leptomeningeal enhancement, attributed to inflammatory or vascular abnormality (i.e. dural arteriovenous fistula). Outpatient lumbar puncture and cerebral angiogram were planned. In August 2023, she returned for sudden onset left leg weakness and numbness. MRI brain showed a new enhancing right parafalcine mass measuring 2.0 x 2.5 cm, radiographically concerning for meningioma but with surrounding vasogenic edema in the frontal and parietal lobes. Given the rapid expansion, differential included granulomatous, inflammatory, or neoplastic process. Pathology showed the mass was an EBV associated malignant spindle cell tumor with molecular studies showing a DICER1 mutation with MDM2 amplification.

When encountering rapid progression of leptomeningeal disease to mass lesion, it is important to consider primary intracranial sarcomas associated with DICER1 mutation. This case elucidates initial pathogenesis of the tumors and may indicate the aggressive nature of the tumor as the DICER1 mutation is not typically seen in combination with the MDM2 epigenetic.