Postoperative histopathology confirmed the diagnosis of Ewing sarcoma of the calcaneus, navicular, cuboid, and cuneiform bones and all metatarsal bones except the first (Figure 7). At 2-year follow-up, the patient had no evidence of local recurrence or distant metastasis based on chest CT and clinical examination of the affected site.
Discussion
Ewing sarcoma is the prototype of round small cell malignancies that arise from the long bones and the flat bones. It seldom involves the hands or feet. To our knowledge, this is the first report of Ewing sarcoma of the foot with multiple-bone involvement. Our literature review found a case of Ewing sarcoma of the first phalanx of the third toe, the second metatarsal bone, the cuneiform, the cuboid, and the talus, with lesser soft-tissue extension compared with our patient’s case.9
As this foot tumor is rare, there are few reports on its clinical aspects, appropriate treatment, and long-term outcome. For treatment of nonmetastatic Ewing sarcoma, limb-salvage surgery is advised if response has been good and there is a reasonable expectation of negative margins and good functional results.
Radiation and surgery may be part of the overall treatment plan. Radiation without surgery has a unique role in pelvic Ewing sarcoma, in contrast to extremity Ewing sarcoma. In our opinion, margins and histologic necrosis in the resection specimen are examined after surgery, and, if the margins are widely negative and histologic response is good, no further local control is advised. If the margin is positive, postoperative radiation therapy is recommended.1 Amputation has gradually become a (rare) choice in the treatment of extremity sarcomas.9 In our patient’s case, surgery was preferred over radiation therapy after chemotherapy because of the low risk of local side effects and the expected high efficacy. In addition, radiation at such high doses for Ewing sarcoma in the foot causes functional impairment. Because of the multiple-bone involvement, a salvage procedure was not possible for our patient. Given the calcaneal involvement, however, below-knee amputation was considered safer than ankle disarticulation.
Multiple-bone involvement occurs in the advanced stage of Ewing sarcoma, usually after visceral and pulmonary metastases are detected.9 The case reported by Rammal and colleagues9 had both multiple-bone involvement in the foot and pulmonary metastasis. The authors indicated that hematogenous spread of the tumor was discerned because the lesions were noncontiguous.9 Our patient had no distant metastases. We think his tumor originated in a tarsal or midtarsal bone and extended to adjacent bones. Therefore, it probably spread through its capsular and ligamentous attachment among tarsal and midtarsal bones, as the involvement was contiguous rather than distinct.
Average delay from symptom onset to diagnosis was reported to be 34 weeks.3 Average physician delay from initial visit to correct diagnosis was reported to be 19 weeks.3 Patients may have erythema, fever, and swelling, suggestive of osteomyelitis.3 Laboratory results may show increased white blood cell count and elevated ESR and CRP level.3 In addition, needle biopsy of the tumor may reveal an appearance grossly similar to that of pus.3 Therefore, physicians may send all the tissue out for microbiological analysis (according to the erroneous diagnosis of infection) and none out for pathologic analysis. The situation can be further complicated when Ewing sarcoma occurs in the foot, an uncommon site. In this special case, multiple-bone involvement can present a misleading clinical picture of infection.10 In other words, infection is one of the best choices in the differential diagnosis.7 Also to be considered are multicentric giant cell tumor, fibrosarcoma,11 and osteosarcoma.12