대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Ewing Sarcoma/Primitive Neuroectodermal Tumors in the mediastinum

Radiologic Findings

Initial chest radiography shows moderate amount of left pleural effusion with contralateral mediastinal shifting and obliteration of left cardiac and diaphragmatic margins on frontal view (Figure 1). There were seen large contour bulging mass opacities in left lower hemithorax on lateral view.
Findings of pre- and postcontrast-enhanced chest CT (Figure 2-5) revealed heterogeneously enhancing (20-80 Hounsfiled unit) well-defined 2 separate large masses, which were located in each anterior and middle mediastinum of the left lower hemithorax. The large one of the masses in left anterior mediastinum was measured about 15 x 9 x 8cm, which showed broad contact with the left chest wall anteriorly, mass effect with compression resulting in contour deformity of the adjacent left cardiac chambers posteromedially on axial scan (Figure 3) and inversion of the left diaphragm inferiorly on coronal scan (Figure 4-5). The other separate smaller mass in the middle mediastinum of the left lower hemithorax was measured about 6 x 7 x 7cm, which was located between posterior wall of the left ventricle and left lateral wall of the descending thoracic aorta on axial and coronal scans (Figure 2-3). Intervening mediastinal fat plane between those masses and adjacent mediastinal structures seemed to be preserved with compression and contour deformity of the left cardiac chambers and no definite evidence of direct tumor invasion.

Excision of the mediastinal masses was performed and the final diagnosis was confirmed.
On gross histopathologic examination, the tumors were seen as multilobulated, friable, soft masses and measuring 19 x 13 x 6cm in the larger one (Figure 8). Microscopically, the tumors revealed lobular growth pattern with hemorrhage and extensive necrosis and were composed of uniform round blue cells with inapparent, small nucleoli, and scanty cytoplasm (Figure 9).

Figure 8

Figure 9

Brief Review

Ewing sarcoma/primitive neuroectodermal tumors (ES/PNET) represent a family of high-grade small round cell tumors, which have neuroectodermal origin and show varying degrees of neuronal differentiation. The Ewing sarcoma family of tumors includes classic Ewing sarcoma of bone, extra-skeletal Ewing sarcoma, Askin tumors of the chest wall, and primitive neuroectodermal tumors of bone or soft tissues.
These highly malignant tumors are reported commonly in children and young adults, which show_80%of patients being in their first 2 decades of life. Extraskeletal ES/PNETs are quite rare than skeletal ES/PNETs and common location of extraskeletal ES/PNETs is thoracopulmonary area. Among the thoracopulmonary ES/PNETs, primary mediastinal ES/PNETs are very rare.
On chest CT scan, ES/PNET usually manifests as a large unilateral heterogeneously enhancing mass, often with low attenuating necrosis or cystic areas and high attenuating hemorrhage. The tumor tends to displace rather than encase adjacent structures such as vessels, the trachea/bronchi, or the mediastinum, which finding also can be well recognized in our case. Calcification of the mass is relatively rare and can be seen in 10 % of the tumors. Lymph node metastasis is also rarely seen. Interestingly, distant metastasis is rare at the time of diagnosis in the thoracopulmonary ES/PNET, but after treatment, including excision, chemotherapy, and local radiation therapy, the tumor shows tendency of frequent local recurrence and distant metastasis as seen in our case. In case of thoracopulmonary ES/PNET, the tumor is frequently associated with adjacent rib or sternum destruction and pleural effusion.
In our case, the mediastinal tumors revealed relatively typical CT features, which include heterogeneously enhancing large masses with areas of low attenuation corresponding tumor necrosis on gross specimen. No calcification was identified and there was no lymph node metastasis at the time of initial diagnosis. Our case presented as separate 2 synchronous masses in each anterior and middle mediastinum at initial diagnosis.
The ES/PNET group of tumors has been known to have poor prognosis. Askin et al reported median survival of only 8 months after the diagnosis of the tumor. However, recent studies show significant improvement in 5-year overall survival of exceeding 60% to 65% for localized ES/PNET with a combination of surgical excision, intense chemotherapy, and high-dose radiotherapy. Most important prognostic factors are known as tumor size, presence of distant metastasis at presentation, and surgical resection margin.

References

1. Zhang WD, Zhao LL, Huang XB, et al. Computed tomography imaging of anterior and middle mediastinal Ewing sarcoma/primitive neuroectodermal tumors. J Thorac Imaging. 2010;25:168–172.
2. El Weshi A, Allam A, Ajarim D, et al. Extraskeletal Ewing’s sarcoma family of tumours in adults: analysis of 57 patients from a single institution. Clin Oncol (R Coll Radiol). 2010;22:374–381.
3. Murphey MD, Senchak LT, Mambalam PK, et al. From the radiologic pathology archives: Ewing sarcoma family of tumors: radiologic-pathologic correlation. Radiographics. 2013;33:803–831.
4. Javery O, Krajewski K, O’Regan K, et al. A to Z of extraskeletal Ewing sarcoma family of tumors in adults: imaging features of primary disease, metastatic patterns, and treatment responses. AJR Am J Roentgenol. 2011;197:W1015–W1022.
5. Dick EA, McHugh K, Kimber C, et al. Imaging of non-central nervous system primitive neuroectodermal tumours: diagnostic features and correlation with outcome. Clin Radiol. 2001;56:206–215.

Please refer to

Case 202 Case 250 Case 354 Case 896 Case 1121

Keywords

mediastinum, primitive Neuroectodermal Tumor (PNET), sarcoma, Ewing sarcoma,