Working Diagnosis:
Biopsy of the presacral mass revealed a malignant small round cell tumor, most consistent with Ewing sarcoma

Treatment:
His bone marrow showed a normocellular bone marrow with no evidence of a metastatic tumor. PET/CT showed no evidence of metastatic disease but did show prominent mesenteric lymph nodes, albeit without increased radiotracer uptake. Since this seemed to be a localized disease, he was started in a randomized control trial that included chemotherapy and radiation therapy.
Case Photo #5

Outcome:
While on consolidation chemotherapy, he complained of left scalp pain and further imaging showed new metastases on the scalp and a T6 vertebral body lesion as well as interval growth of his presacral mass. He underwent salvage chemotherapy and additional radiation therapy, but after 1 month, his presacral mass was still growing. He obtained a second opinion and was briefly started on pazopanib, before ultimately deciding to pursue hospice.

Author's Comments:
This case, unfortunately, showed how difficult it is to diagnose Ewing sarcoma. This patient initially had hamstring pain and was not diagnosed with Ewing sarcoma until he came to our sports medicine clinic. At that time, he had already developed neurologic symptoms including the foot drop and sensory deficits. Primary bone tumors, like Ewing Sarcoma, represent 6% of all childhood cancers and are very aggressive, with a five-year survival rate of 33% if metastasis is present (1). Subclinical metastatic disease is presumed to be present in nearly all patients with Ewing Sarcoma. Approximately 200 children and adolescents are diagnosed each year in the United States with Ewing Sarcoma, with a peak incidence at 10-15 years old (2). Since constitutional symptoms are only present in 10-20 percent of patients at diagnosis, providers should have a high degree of suspicion for malignancy in this age group, especially if neurologic symptoms are also present. The most common locations for Ewing Sarcoma include the long bones of the extremities and pelvis, resulting in localized pain and swelling (1).

Editor's Comments:
Clinicians should maintain a broad differential when evaluating pediatric patients with non traumatic pain complaints and identify red flags that warrant aggressive workup. In this case, multiple red flag findings were appropriately noted including 4 weeks or more of daily pain, pain that worsened, neurological deficits, and night pain. As noted in this case, 5 year survival rate is low when metastatic disease is present but can increase to 70 to 80% for localized disease highlighting a potential benefit to early detection (3,4)

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