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Special Feature
May 1, 2008

Image of the Month—Diagnosis

Arch Surg. 2008;143(5):512. doi:10.1001/archsurg.143.5.512

Answer: Retroperitoneal Extraskeletal Ewing Sarcoma

A computed tomographic–guided fine-needle aspiration biopsy specimen obtained from the lesion revealed small and round blue cells with round nuclei, small nucleoli, and scanty cytoplasm, which seemed to be well organized. Immunohistochemical analysis revealed intense staining for CD99, CAM 5.2, epithelial membrane antigen, and anti–cytokeratin antibodies AE1/AE3, and negative staining for FLI-1, desmin, and leukocyte common antigen.

Based on these findings, the diagnosis was consistent with an extraskeletal Ewing sarcoma (EES) or primitive neuroectodermal tumor.

In accordance with the oncologists, the patient received 2 cycles of neoadjuvant chemotherapy according to the CEVAIE regimen (carboplatin, etoposide phosphate, vincristine, actynomicin D, ifosfamide, and epirubicine hydrochloride). On restaging magnetic resonance imaging, significant tumor shrinkage was reported, with a maximum diameter of the lesion of 7.5 cm; the tumor continued to infiltrate the left renal parenchyma, left renal vascular structures, and left adrenal gland and involved the pancreatic tail.

At laparotomy (Figure 2), a grossly apparently necrotic lesion was found and excised en bloc with the left kidney and adrenal gland, pancreatic tail, spleen, and descending colonic flexure. Definitive histologic examination findings confirmed the diagnosis of EES, with a reduction of 85% with respect to the original tumor bed. The colon, left adrenal gland, spleen, and pancreas were microscopically free from tumor invasion. Because no skeletal involvement was demonstrated, the perirenal fat was considered the origin of this tumor.

Figure 2. 
An intraoperative photograph demonstrating a grossly necrotic well-encapsulated mass in the left hypochondrium, close to the descending colonic flexure and just below the pancreatic tail.

An intraoperative photograph demonstrating a grossly necrotic well-encapsulated mass in the left hypochondrium, close to the descending colonic flexure and just below the pancreatic tail.

The postoperative course was uneventful, and the patient was discharged from the hospital on the 11th postoperative day.

Radiation therapy was commenced at a dose of 50.4 Gy (5040 rad) in 28 fractions of 1.8 Gy (180 rad), and concurrent chemotherapy was started. The patient is alive, with no clinical and radiological evidence of recurrence within 24 months of follow-up.

Ewing sarcoma is the second most common primary osseous malignant neoplasm in childhood and adolescence1but rarely may have an extraskeletal origin. Extraskeletal Ewing sarcoma can be confused with other small, round, blue cell tumors, including embryonic rabdomyosarcoma, lymphoma, and neuroblastoma. This tumor, even if considered a distinct entity, shares histologic, immunohistochemical, and molecular findings with Ewing sarcoma of bone.2A sensitive and relatively specific antigen, CD99/MIC-2, and a characteristic chromosomal translocation, t(11;22)(q24;12), have been identified in skeletal ES and EES.2

Extraskeletal Ewing sarcoma rarely involves the retroperitoneum. In a review of 24 EESs,3the authors found only 2 patients presenting with EES involving the retroperitoneum; in both cases, patients received only a palliative treatment with chemotherapy, with a follow-up of only 4 and 5 months, respectively. The most effective treatment is surgery combined with chemotherapy and high-dose radiation therapy.4When resectable, the surgical excision must be wide in accordance with the classic oncologic principles, and radiation therapy should be used as an adjuvant to resection in an attempt to improve local control, whereas chemotherapy should be considered preoperatively, in an attempt to shrink the tumor, and postoperatively, in an attempt to address the obscure systemic disease. Overall and disease-free survival have improved significantly in recent years, obtaining important results (77% and 55%, respectively) when multimodal therapy is used.5Retroperitoneal EES is a rare tumor but should always be considered in the differential diagnosis of any patient, of any age, with a soft tissue mass of the retroperitoneum. Even patients presenting with extensive involvement may benefit from an aggressive multimodal management strategy involving surgery, chemotherapy, and radiation therapy.

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Correspondence:Fausto Rosa, MD, Digestive Surgery Unit, Department of Surgical Sciences, Istituto di Clinica Chirurgica, Catholic University School of Medicine, Largo A. Gemelli, 8, 00168 Rome, Italy (faust.rosa@tiscali.it).

Accepted for Publication:December 13, 2006.

Author Contributions:Study concept and design: Rosa. Acquisition of data: Tortorelli and Papa. Analysis and interpretation of data: Pacelli and Doglietto. Drafting of the manuscript: Rosa and Papa. Critical revision of the manuscript for important intellectual content: Rosa, Tortorelli, Pacelli, and Doglietto. Administrative, technical, and material support: Rosa. Study supervision: Rosa, Tortorelli, Pacelli, and Doglietto.

Financial Disclosure:None reported.

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