Primary intracranial extraosseous Ewing’s sarcoma of the skull base in an elderly adult: illustrative case

Abstract

BACKGROUND Primary extraosseous intracranial Ewing’s sarcoma, also known as a peripheral primitive neuroectodermal tumor or “small round blue cell tumor,” is an extremely rare entity with limited representation in the literature beyond the pediatric population. OBSERVATIONS A 67-year-old male suffering occipital headache, nausea, and gait disturbance was found to have a large, avidly contrast-enhancing cerebellopontine angle mass extending into the cervical spinal canal with associated mass effect on medulla, cerebellum, fourth ventricle, and cervical spinal cord. This mass was not present on the imaging from 8 years prior. He underwent surgical debulking and pathology results demonstrated a malignant small round cell tumor showing diffuse immunopositivity for cytokeratins, CD99 and NKX2.2 with EWRS1-FLI1 rearrangement in 84% of the nuclei confirmatory of Ewing’s sarcoma. After 14 cycles of chemotherapy and 6 weeks of radiotherapy, 22 months after discovery, the patient remains in clinical and radiographic remission with complete return to his baseline functioning. LESSONS Primary skull base extraosseous Ewing’s sarcoma should be considered in the differential diagnosis even in the elderly population when imaging studies demonstrate aggressive tumor growth patterns. Tumor debulking to establish a diagnosis followed by adjuvant chemoradiation therapy can result in clinical improvement with remission.

Primary intracranial peripheral primitive neuroectodermal tumor: lessons from an exceptionally rare neoplasm. Illustrative case

“…Accounting for 0.03% of intracranial tumors and 1% to 2% of EWS cases, pPNETs are extremely rare malignant neoplasms. 2,6,[13][14][15][16][17] Demographically, children and adolescents are commonly affected. 2,[17][18][19] MRI findings commonly show heterogeneous and hypo-to isointense lesions on T1-weighted sequences and iso-to hyperintense lesions on T2-weighted sequences.…”

“…3,4 pPNET frequently affects children and young adults, whereas middle-aged adult and elderly populations have shown a low prevalence. [5][6][7] Symptoms from this condition are unspecific, vary depending on the tumor location, and can be secondary to mass effect (e.g., seizures, neurological deficits, vomiting, and headaches). 5 The scarcity of reports, the broad differential diagnosis, and optimal therapy are among the most notable challenges in understanding pPNET comprehensively.…”