This composite educational image illustrates the multimodal diagnostic features of Ewing sarcoma, a malignant primary bone tumor. Panel A displays an anteroposterior X-ray of a pediatric femur showing an expansile, permeative, and destructive lesion within the diaphysis, marked by white arrows. Panel B provides a histopathological view (H&E stain, 400x magnification) revealing a dense proliferation of monomorphic 'small round blue cells' characterized by high nuclear-to-cytoplasmic ratios and scanty cytoplasm, arranged in sheets. Panel C demonstrates a break-apart Fluorescence in situ Hybridization (FISH) assay used for molecular confirmation. The presence of separated red (5'-EWSR1) and green (3'-EWSR1) fluorescent signals (white arrows) indicates a chromosomal rearrangement of the EWSR1 locus on chromosome 22, while fused orange signals represent intact alleles. This progression from gross radiology to cellular morphology and molecular genetics highlights the integrated diagnostic approach required for bone sarcomas in children and young adults.

This composite diagnostic image features an anteroposterior X-ray (left) and a coronal CT reconstruction (right) of a pediatric humerus following limb-salvage surgery for Ewing’s sarcoma. The image demonstrates a 3D-printed, custom-made hollow prosthesis replacing the proximal and mid-diaphysis of the humerus while preserving the distal native bone and elbow joint. The prosthesis exhibits a distinctive porous structure with multiple radiolucent perforations throughout its radiopaque shell, designed to facilitate revascularization of internal bone grafts from surrounding soft tissues. The distal end of the implant features a wide collar that circumferentially overlaps the remaining humeral bone, secured by multiple transverse screws. The CT scan confirms the hollow nature of the internal chamber, which is packed with morselized allograft cortico-cancellous bone chips, visible as heterogenous, semi-dense material within the high-density prosthetic shell. This setup highlights orthopedic oncological techniques for pediatric reconstruction, focusing on biological integration and joint preservation.

Anteroposterior X-ray of the proximal humerus showing an aggressive, intramedullary osteolytic lesion. The lesion is primarily located within the metaphysis and extends into the proximal diaphysis. It exhibits a mottled, permeative appearance with poorly defined, irregular borders, indicating a narrow zone of transition. There is evidence of cortical thinning and a 'moth-eaten' pattern of bone destruction, characteristic of malignant processes such as Ewing sarcoma. A red arrow highlights the area of most significant radiolucency and architectural disruption within the medullary canal. The image demonstrates key radiological signs used in orthopedic oncology to differentiate aggressive primary bone tumors from benign lesions.