대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Extraskeletal Ewing's Sarcoma / PNET of the pleura

Radiologic Findings

Fig a. Chest CT shows a large paravertebal mass with internal low-density areas. Multiple subpleural masses suggesting pleural seeding is also seen in the right hemithorax.

Fig b. T2-weighted FSE MR imaging shows a large paravertebral mass with internal cystic spaces. Multiple pleural nodules and large amount of effusion are found in the right hemithorax.

Fig c. T1-weighted coronal MR imaging shows focal high signal intensity within the mass suggesting hemorrhagic foci.

Fig d. Gadolinium-enhanced T1-weighted axial MR imaging shows marked enhancement of the tumor.

Fig e. Photomicrograph (x400) shows small round cells and pseudorossette formation.

Fig f. Photomicrograph shows intense membranous immunoreactivity for CD99.

Brief Review

Askin tumor characterized by malignant small cell tumors that appeared to originate in the soft tissue of the chest wall or the periphery of the lung was firstly described in children and adolescents (1). This lesion, also known as primitive neuroectodermal tumor (PNET), is now recognized as an aggressive type of Ewing sarcoma. Ewing sarcoma or PNET is found most often in children and young adults. They probably develop from embryonal neural crest cells and contain the same balanced reciprocal translocation t(11;22)(q24;q12). The translocation point has been cloned and is identical in the two tumor types (2,3).

CT scans of Ewing sarcoma typically show a large ill-defined mass with an inhomogeneous appearance caused by extensive cystic degeneration (Figs a-b), which may or may not be accompanied by calcification (4). On T1-weighted MR images, tumors generally have signal intensity equal to or greater than that of muscle. Larger tumors appear as heterogeneous masses, frequently with evidence of hemorrhage or necrosis (Fig c), whereas smaller ones tend to be more homogeneous. On T2-weighted images, the tumors tend to have inhomogeneous high signal intensity. Tumors show marked enhancement after intravenous administration of contrast material. Hemorrhage is a frequent microscopic finding (5) (Fig d).

References

1. Askin FB, Rosai J, Sibley RK, Dehner LP, McAlister WH. Malignant small cell tumor of the thoracopulmonary region in childhood: a distinctive clinicopathologic entity of uncertain histogenesis. Cancer 1979; 43:2438-2451.

2. Dehner LP. Primitive neuroectodermal tumor and Ewing’s sarcoma. Am J Surg Pathol 1993; 17:1-13.

3. Ladanyl M, Heinemann FS, Huvos AG, Rao PH, Chen QG, Jhanwar SC. Neural differentiation in small round cell tumors of bone and soft tissue with the translocation t(11;22)(q24;q12): an immunohistochemical study of 11 cases. Hum Pathol 1990; 21:1245-1251.

4. Winer-Muram HT, Kauffman WM, Gronemeyer SA, Jennings SG. Primitive neuroectodermal tumors of the chest wall (Askin tumors): CT and MR findings. AJR Am J Roentgenol 1993; 161:265-268.

5. O'Keeffe F, Lorigan JG, Wallace S. Radiological features of extraskeletal Ewing sarcoma. Br J Radiol 1990; 63:456-460.

Keywords

Pleura, Malignant tumor,