Diagnosis Ewing's sarcoma

micrograph of metastatic ewing s sarcoma characteristic cytoplasmic clearing on h&e staining, showing pas positive.

the definitive diagnosis based on histomorphologic findings, immunohistochemistry , molecular pathology.

ewing s sarcoma small-blue-round-cell tumor typically has clear cytoplasm on h&e staining, due glycogen. presence of glycogen can demonstrated positive pas staining , negative pas diastase staining. characteristic immunostain cd99, diffusely marks cell membrane. morphologic , immunohistochemical findings corroborated associated chromosomal translocation, of several occur. common translocation, present in 90% of ewing sarcoma cases, t(11;22)(q24;q12), generates aberrant transcription factor through fusion of ewsr1 gene fli1 gene.

the pathologic differential diagnosis grouping of small-blue-round-cell tumors, includes lymphoma, alveolar rhabdomyosarcoma, , desmoplastic small round cell tumor, among others.

differential diagnosis

other entities similar clinical presentations include osteomyelitis, osteosarcoma (especially telangiectatic osteosarcoma), , eosinophilic granuloma. soft-tissue neoplasms such pleomorphic undifferentiated sarcoma (malignant fibrous histiocytoma) erode adjacent bone may have similar appearance.

imaging findings

x-ray of child ewing s sarcoma of tibia



magnetic resonance imaging slice showing ewing s sarcoma of left hip (white area shown right)

on conventional radiographs, common osseous presentation permeative lytic lesion periosteal reaction. classic description of lamellated or onion-skin type periosteal reaction associated lesion. plain films add valuable information in initial evaluation or screening. wide zone of transition (e.g. permeative) useful plain film characteristic in differentiation of benign versus aggressive or malignant lytic lesions.

magnetic resonance imaging (mri) should routinely used in work-up of malignant tumors. show full bony , soft tissue extent , relate tumor other nearby anatomic structures (e.g. vessels). gadolinium contrast not necessary not give additional information on noncontrast studies, though current researchers argue dynamic, contrast-enhanced mri may determine amount of necrosis within tumor, in determining response treatment prior surgery.

computed axial tomography(ct) can used define extraosseous extent of tumor, in skull, spine, ribs, , pelvis. both ct , mri can used follow response radiation and/or chemotherapy. bone scintigraphy can used follow tumor response therapy.

in group of malignant small round cell tumors include ewing s sarcoma, bone lymphoma, , small cell osteosarcoma, cortex may appear normal radiographically, while permeative growth occurs throughout haversian channels. these tumours may accompanied large soft-tissue mass while no bone destruction visible. radiographs not shown signs of cortical destruction.

radiographically, ewing s sarcoma presents moth-eaten destructive radiolucencies of medulla , erosion of cortex expansion.