Summary: Prepared by Terrence J. Barrett, DO, Justin Q. Ly, MD, and Steven W. Davis, MD, Wilford Hall Medical Center, Lackland AFB, TX; Douglas P. Beall, MD, Department of Radiology and Nuclear Medicine, The Uniformed Services Health Sciences University, Bethesda, MD; and Christian L. Carlson, MD, Department of Radiology, Brooke Army Medical Center, San Antonio, TX.
Summary: A 7-year-old girl presented with 5 months of pain and swelling of her right lower extremity. A physical examination revealed focal edema and point tenderness over the region of her right proximal fibula. The patient also reported generalized symptoms of fever, malaise, and mild anemia.
Diagnosis
Ewing's sarcoma with distant osseous metastasis
Findings
Lower extremity radiography (Figure 1) was performed, revealing a permeative osseous lesion involving the proximal right fibula that showed an aggressive periosteal reaction. The characteristic radiographic findings of a permeative diaphyseal process associated with an aggressive "onionskin" type of periostitis suggests the diagnosis of a bone tumor (Figure 1). Pain in the right pelvis area prompted a pelvic radiograph, which further revealed a lytic, rounded lesion of the right iliac wing, abutting the right sacroiliac joint (Figure 2). The lesion showed no significant matrix. The multiplicity of lesions suggested a metastatic process, which was further supported by increased uptake in the fibula and pelvis on osseous scintigraphy (not shown). The primary malignancy was believed to arise from the proximal fibula, with secondary involvement of the right ilium. No other metastatic foci were detected. In this partient, the appropriate clinical evidence, including signs, symptoms, and patient age, were also suggestive of Ewing's sarcoma. MR imaging of the distal lower extremity showed its impressive soft issue invasion (Figure 3). Definitive diagnosis was determined with a biopsy, which revealed the small, blue round cells of Ewing's sarcoma (Figure 4). Subsequent to diagnosis, the patient underwent wide local excision with adjuvant chemotherapy.
Discussion
Although malignant bone tumors are uncommon in children, they pose a significant diagnostic and therapeutic challenge to clinicians. Radiologic advances have allowed more thorough evaluation of these tumors. MR imaging has improved the ability to assess tumor margins and more accurately stage these lesions.1 Computed tomography and conventional radiography are often used in the initial evaluation of bone tumors, and osseous scintigraphy is the study of choice for the evaluation of suspected metastases, which are a relatively common phenomenon. Along with bone scanning, these 2 modalities are also used in the diagnosis of distant metastasis of these tumors, which is a very common finding.
Ewing's sarcoma was first identified by Dr. Ewing in the 1920s.2 As the second most common pediatric bone tumor, it most frequently develops in the axial skeleton, particularly in the pelvis.1 The diaphyses of the femur, tibia, and humerus are also common sites of primary tumor involvement.1,3 Approximately 70% of cases have disseminated disease with involvement of multiple osseous and visceral sites (lung and bone marrow are most common) in the later course of the disease.1,4 Roughly 10% have multiple lesions at diagnosis, which could be multiple primaries or a primary lesion with metastases.3 Imaging findings often resemble those of osteosarcoma, and definitive diagnosis is made by biopsy and histological evaluation.
The classic radiographic appearance of Ewing's sarcoma is onionskin periostitis and is often used as a preliminary means of differentiating these tumors. The spiculated or "sunburst" type of periosteal reaction can also be seen with Ewing's sarcoma, but is more often seen in osteosarcoma.5 Recent advances in MR imaging have contributed to the staging of these tumors by allowing soft tissue visualization, especially of the nearby neurovascular structures.3 Staging helps to minimize mistakes in biopsy and aids in the treatment of these lesions.3 Staging with MR imaging can often eliminate the need for total limb amputation by giving the clinician the exact location and extent of the disease and can also be used to access the tumor response to therapy.
The recommended treatment of Ewing's sarcoma is surgical resection or radiation ablation of the primary tumor, followed by multidrug chemo therapy for possible distant metastasis.3 Resectable extremity lesions have a more favorable outcome than do axial skeletal lesions.1 However, despite treatment, these tumors are often recurrent and metastatic.
CONCLUSION
The "onionskin" periostitis is classic for Ewing's sarcoma. The MR appearance is often a large soft-tissue mass. The definitive diagnosis is made by biopsy, and a close look for metastatic lesions at the time of presentation is appropriate.
- Himelstein BP, Dormans JP. Malignant bone tumors of childhood. Pediatr Clin North Am.1996; 43:967-984.
- Dorfman, HD, Czerniak B. Bone Tumors.St. Louis, MO: Mosby; 1998.
- Miller SL, Hoffer FA. Malignant and benign bone tumors. Radiol Clin North Am. 2001;39:673-699.
- Fechner R, Mills S. Tumors of the bones and joints. In: Rosai J, ed. Atlas of Tumor Pathology.Third Series, Fascicle 8. Washington, DC: Armed Forces Institute of Pathology; 1993:187-195.
- Garber CZ. Reactive bone formation in Ewing's sarcoma. Cancer.1951;4:839-845.