Ewing sarcoma of the temporal bone with aneurysmal bone cyst-like changes: A rare case report with an unusual radiological presentation

Abstract

Ewing sarcoma (ES) is a malignant small round cell tumor, accounting for 10-15% of all primary bone tumors and approximately 3% of all pediatric cancers. Primary ES of the cranial bone is unusual with reported incidence from 1% to 6% of all ES cases. This report shows a rare case of primary ES of the squamous temporal bone in a 12-year-old boy with a history of swelling of the right temporal region and symptoms of increased intracranial pressure. We illustrate the extremely unusual radiological presentation of this primary ES of temporal bone associated with large aneurysmal bone cyst-like (ABC-like) changes. The boy was successfully treated according to Euro Ewing 2012 protocol. He is alive with no evidence of recurrence and metastasis after 16 months of completed treatment.

Keywords: CT; Ewing sarcoma; MRI; skull; temporal bone.

Figue 1.

Multiparametric magnetic resonance imaging (MRI) shows a tumor arising from the squamous part of right temporal bone with a small extracranial soft-tissue mass and a large intracranial soft-tissue mass compressing the brain structures. The small extracranial soft-tissue mass (white arrowhead) reveals homogeneous intermediate signal intensity on axial T2W imaging (a), high signal intensity on axial diffusion-weighted imaging (DWI, b = 1000 s/mm²) with a corresponding low apparent diffusion coefficient value (ADC: 0.7 × 10⁻³ mm²/s) (b), (c), and homogeneous contrast enhancement on postgadolinium axial T1W imaging (d). The large intracranial soft-tissue mass mainly contains blood-filled spaces of variable size with fluid–fluid levels on T2W, axial DWI (b = 1000 s/mm²), and ADC images (e)–(g), and smooth septal and rim contrast enhancement (h), suggesting ABC-likes changes (white arrows). Axial and coronal CT (i), (j) images show an ill-defined, permeative bone destruction in the squamous part of right temporal bone. Aggressive spiculated periosteal reaction and expanded cortex with Codman triangle (white arrowhead).

Figure 2.

(a) H&E (×100) staining showing cystic appearing areas with rest of vital small round cells. (b) Immunohistological staining with CD99 confirming that the round cells represent rest of Ewing sarcoma.

Figure 3.

Follow-up MRI, 4 months after the initiation of neoadjuvant chemotherapy and before surgery, shows full regression of extracranial soft-tissue mass and partial regression of the intracranial soft-tissue mass. The intracranial component showed areas reminiscent of ABC-likes changes (blood-filled spaces with hemosiderin contain) on axial T2W imaging (a) and on axial susceptibility weighted imaging (SWI) (b). No areas of high signal intensity on axial DWI (b = 1000 s/mm²) (c), and septal and rim contrast enhancement near temporal bone on axial postgadolinium T1W imaging (d), indicating some viable residual tumor tissue.