Extraskeletal Ewing Sarcoma of the Chest Wall Manifesting as a Palpable Breast Mass: Ultrasonography, CT, and MRI Findings

Abstract

Ewing sarcomas constitute a group of small, round, blue cell tumors of the bone and soft tissue. Extraskeletal Ewing sarcoma (EES) is a rare malignant neoplasm that arises from soft tissues, and it usually affects children and young adults. EES of the thoracopulmonary region commonly presents with a palpable mass or pain. Although rarely reported, EES affecting the anterior chest wall may present as a breast mass. We report a case of EES arising from the chest wall and manifesting as a palpable breast mass in a 22-year-old woman. The large mass was initially misdiagnosed as a breast origin mass on ultrasonography, but subsequent CT and MRI showed that the mass originated from the chest wall. Radiologists should be aware of the imaging findings of EES, and they should understand that chest wall lesions may be clinically confused as breast lesions.

Keywords: Chest Wall; Computed Tomography, X-Ray; Ewing Sarcoma; Magnetic Resonance Imaging; Ultrasonography.

Fig. 1. A 22-year-old woman with Ewing sarcoma arising from the chest wall and presenting as a palpable mass in her right breast.

A. Ultrasonography image reveals a large, oval, complex cystic, and solid mass. The mass shows heterogeneous internal echogenicity, and multiloculated cystic components are mainly located within the superficial area of the mass (arrows) (left image). There is internal vascularity within the solid portion of the mass on color Doppler ultrasonography (right image). B. A contrast-enhanced chest CT axial image with a mediastinal window setting shows a multilobulated and heterogeneously enhancing mass with multiple cystic components in the right chest wall. The mass shows a focal extension to the intrathoracic area (arrowheads) (left image). Axial CT scan with bone window setting demonstrates the destruction of the adjacent right fifth rib (arrow) (right image). C. MRI, after the sixth cycle of neoadjuvant chemotherapy, reveals an oval, circumscribed, and heterogeneous mass in the right pectoralis major muscle. The mass shows multiloculated, heterogeneously iso- to high signal intensity fluid collections of various phase hemorrhages on a T2-weighted image (upper left panel) and an intermediate signal intensity (isointense to adjacent muscle) with high signal intensity foci representing a hemorrhage on a T1-weighted image (upper right panel) show heterogeneous enhancement within the solid portion of the mass and a focal extension to the thoracic cage (arrowheads) with rib destruction (arrow). D. Gross and microscopic findings. The tumor is well-circumscribed, grayish brown, and soft, with focal hemorrhaging and a cystic area (upper left panel). The tumor is composed of sheets of uniform, small, round cells (hematoxylin and eosin stain, × 200) (upper right panel). The tumor cells show diffuse membranous positivity for CD 99 (lower left panel) and diffuse nuclear positivity (lower right panel) (immunohistochemical stain, × 200).