Central nervous system extraosseous Ewing sarcoma: radiologic manifestations of this newly defined pathologic entity

Abstract

Although these entities are histologically similar, recent advances in molecular genetics have allowed the distinction of central nervous system extraosseous Ewing sarcoma (CNS-EES) from central primitive neuroectodermal tumors (c-PNET) including medulloblastoma and supratentorial PNET. We present 2 cases of pathologically confirmed CNS-EES. Knowledge of CNS-EES as a distinct entity enables the neuroradiologist to suggest the proper diagnosis and the need for special immuno-histochemical and molecular studies to confirm the diagnosis. Because treatment and prognosis are vastly different, the proper diagnosis of CNS-EES versus c-PNET is critical.

Fig 1.

A, Unenhanced CT image demonstrates a 2.4 × 3.8-cm hyperattenuated, well-circumscribed, extra-axial mass centered on the right tentorium. B, Precontrast axial T1-weighted MR image reveals a heterogeneously hyperintense mass with a broad tentorial attachment. C, Postcontrast coronal T1-weighted image reveals a homogeneously enhancing mass demonstrating a smooth lobular contour, with both infratentorial and supratentorial components. D, Hyperintense signal intensity on DWI is seen within the medial aspect of the lesion.

Fig 2.

A, Precontrast axial T1-weighted image reveals a 8.0 × 8.0-cm predominantly hyperintense lobular medial right frontal lobe mass that was large enough to obscure the distinction between an intra-axial or extra-axial mass lesion. B, Postcontrast axial T1-weighted image demonstrates diffuse heterogeneous enhancement. C, Axial T2-weighted image with diffuse heterogeneous signal intensity D, Predominantly hyperintense signal intensity on axial DWI.