A young girl presented with swelling of right thigh, with history of trauma 2 months back. Now she presents with swelling at mid-shaft of femur & low grade fever. ESR is mildly raised. X-ray shows a laminated periosteal reaction. Next line of investigation would be:

MR1 Age group, swelling at mid-shaft of .femur, low grade .fever, mildly raised ESR & laminated periosteal reaction; all point towards the diagnosis of Ewing's sarcoma. But Osteomyelitis can also be put in d/d. Only point which goes against osteomyelitis is the location i.e. the mid-shaft of femur. Osteomyelitis is commonly seen at metaphysis, although diaphysis can be rarely involved. Grainger writes-"The differential diagnosis of Ewing's sarcoma includes osteomyelitis, other lyric bone lesions, osteosarcorna and metastases from another primary tumour. The routine imaging algorithm of these patients includes plain radiography and MRI of the primary lesion, bone scintigraphy of the skeleton looking for metastatic bone spread and plain radiography and CT for chest evaluation of metastases." "When a large soft-tissue mass is present it can still be difficult to differentiate between tumour and infection, even with Gadolinium enhancement. The diagnosis is made by biopsy." In this case X ray has already been done. Next investigation should be MRI (or CT; MR is better). MRI is ideally suited for evaluating the soft tissues, the intramedullary extent of disease, and adjacent soft-tissue involvement of the primary lesion and is an essential pa of the evaluation of a patient with Ewing's sarcoma. Biopsy is done to confirm the diagnosis and rule out osteomyelitis and other bone tumors.Bone scintigraphy is done to look for bone metastases.CT chest is done to look for any lung metastasis. Ewing's sarcoma: Ewing's sarcoma of bone is a highly anaplastic, small, round cell tumor of neuroectodermal origin. It is an aggressive malignancy with a high local recurrence and metastatic rate. Ewing sarcoma is the second most common primary malignancy of bone (after osteosarcoma) in patients younger than 30 years of age and the most common in patients younger than 10 years of age. The most common locations include the metaphyses of long bones (often with extension into the diaphysis) and the flat bones of the shoulder and pelvic girdles. Ewing sarcoma is exceedingly rare in individuals of African descent. Clinical findings: Pain is an almost universal complaint of patients with Ewing sarcoma. Usually the onset is insidious, and the pain may be of long duration before the patient seeks medical attention, The pain may be only mild and intermittent initially and may respond to initial conservative treatment. In addition to pain, patients also may have fever, erythema, and swelling suggesting osteomyelitis. Diagnosis: Laboratory studies may reveal an increased white blood cell count, an elevated erythrocyte sedimentation rate, and an elevated C-reactive protein. Ewing sarcoma appears radiographically as a central lytic tumor of the diaphyseal-metaphyseal bone. It creates extensive permeative destruction of coical bone, and as it breaks through under the periosteum, it takes on a typical onionskin, multilaminated appearance; however, this is not pathognomonic for Ewing's sarcoma. Radiating spicules of new bone in a sunburst pattern (sun-ray appearance) can also occur, making radiographic differentiation from osteosarcoma difficult. Saucer-shaped destruction of the exterior coex is a fairly characteristic feature. Regardless of the location, MRI of the entire bone should be ordered to evaluate the full extent of the lesion, which typically extends beyond the abnormality apparent on plain films. MRI also is useful to evaluate the extent of the soft-tissue mass, which often is very large. All patients should have a baseline radiograph and a CT scan of the chest because the lung is the most common site of metastases. A bone scan should be performed because bone is the second most common site of metastases. Histologically, Ewing sarcoma consists of small blue cells with very little intercellular matrix. Cytogenetic or immunohistochemical studies often are required to differentiate Ewing sarcoma from other small blue cell tumors. The t(11;22)(q24;q12) is the most common translocation diagnostic of Ewing sarcoma and is present in greater than 90% of cases. Immunohistochemical staining for the MIC2 gene product has been repoed to be specific for Ewing sarcoma. In addition, Ewing sarcomas usually are periodic acid-Schiff positive (owing to intracellular glycogen) and reticulin negative. This is in contrast to lymphomas, which are periodic acid-Schiff negative and reticulin positive. Treatment The prognosis is always poor and surgery alone does little to improve it. Radiotherapy has a dramatic effect on the tumor but overall survival is not much enhanced. Chemotherapy is much more effective. The best results are obtained by a combination of all three methods: a course of preoperative neoadjuvant chemotherapy; then wide excision if the tumor is in a ourable site, or radiotherapy. .followed by local excision if it is less accessible,. and then a. fuher course of chemotherapy.for 1 year. Postoperative radiotherapy may be added if the resected specimen is found not to have a sufficiently wide margin of normal tissue.