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• Imaging Techniques

• Imaging Techniques. Computed Tomography. • Magnetic Resonance Imaging. EWING SARCOMA. Radiographic Findings • Radiography o Ill-defined, lytic intramedullary lesion with permeative/moth eaten bone destruction. o Prominent periosteal reaction of "onion skin" or

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• Imaging Techniques

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  1. • Imaging Techniques Computed Tomography • Magnetic Resonance Imaging

  2. EWING SARCOMA

  3. Radiographic Findings • Radiography o Ill-defined, lytic intramedullary lesion with permeative/moth eaten bone destruction o Prominent periosteal reaction of "onion skin" or "sunburst" type, Codman triangle o Cortical erosion, sclerosis, thickening o Saucerization of cortex due to periosteal destruction and extrinsic pressure from soft tissue mass o Penetration into soft tissue with extraosseous, noncalcified, soft tissue mass (50%) o No tumor matrix o Can be sclerotic in flat bones

  4. • Tl C+ o To differentiate tumor from peri tumoral edema o Enhancement of cellular areas • To assess intra- and extraosseous extent

  5. Angiographic Findings • Hypervascular mass Nuclear Medicine Findings • Bone Scan o Intense radiotracer uptake o For evaluation of skeletal metastases • PET o Increased FDG uptake of tumor and metastases o Helpful in assessing response to therapy o To differentiate tumor recurrence from post therapeutic changes

  6. I DIFFERENTIAL DIAGNOSIS Osteomyelitis • May look identical • Duration of symptoms usually shorter « 2 weeks) Langerhans Cell Histiocytosis (LCH) • Solid periosteal reaction • Less aggressive appearance Osteosarcoma • Usually involves metaphyses • Bone formation within destructive lesion and soft tissue Lymphoma • Older age group • Late cortical destruction Metastatic Neuroblastoma • Patients younger than 5 years • Multifocal Primitive Neuroectodermal Tumor (PNET) • Clinically, radiologically, and histologically very similar to Ewing sarcoma • Can not be differentiated from Ewing sarcoma by imaging

  7. Staging, Grading or Classification Criteria • Surgical staging system for malignant musculoskeletal tumors o Stage IA: Low grade, intracompartmental o Stage IE: Low grade, extracompartmental o Stage IIA: High grade, intra compartmental o Stage lIB: High grade, extracompartmental o Stage IlIA: Low or high grade, intra compartmental, metastases o Stage I1IB:Low or high grade, extra compartmental, metastases

  8. OSTEOSARCOMA

  9. Radiographic Findings o Conventional osteosarcoma: 85% • Poorly-defined, intramedullary mass, extends through cortex • Moth-eaten bone destruction • Aggressive periosteal reaction: Codman triangle, sunburst pattern • Indistinct borders with wide zone of transition • Soft tissue mass +/- tumor calcification o Telangiectatic osteosarcoma: < 5% • Was thought to have worst prognosis, but prognosis is likely similar to conventional OGS • Purely lytic lesion • Cystic cavities filled with blood/necrosis • Fluid levels (may mimic aneurysmal bone cyst - ABC) o Multicentric osteosarcoma: 1% • Synchronous osteoblastic osteosarcoma at multiple sites (usually symmetric) • Exclusively in children (5-10 years) • Extremely poor prognosis

  10. o Parosteal osteosarcoma: 3% • Low grade osteosarcoma in older age group (20 - 50 years) • Posterior distal femur • Attached to underlying cortex at origin o Periosteal osteosarcoma: 1% • Intermediate-grade osteosarcoma • Most common diaphyseal • No medullary involvement • Cortical thickening o Gnathic osteosarcoma: S-9% • Involvement of mandible, maxilla • Sclerotic, lytic, mixed • Periosteal reaction • Soft tissue extension o Secondary osteosarcoma: S% • Arises in association with preexisting lesion of bone such as Paget disease, prior radiation, bone infarct

  11. CT Findings • NECT o Helpful in imaging surface OGS o Can show complex anatomy in gnathic OGS • CECT o Enhancement of solid components • Helpful in differentiating telangiectatic OGS from ABC • Telangiectatic OGS: Nodular peripheral enhancement MR Findings • TlWI o Low signal intensity: Mineralized tumor o Low-intermediate signal intensity: Solid, nonmineralized tumor • T2WI o Low signal intensity: Mineralized tumor o High signal intensity: Nonmineralized tumor, soft tissue mass • STIR: Helpful in imaging entire bone to detect skip lesions, multicentric OGS

  12. !DIFFERENTIAL DIAGNOSIS Ewing Sarcoma • Diaphysis of long bone • Large soft tissue mass Osteomyelitis • No bone formation • Sequestrum Chondrosarcoma • Ring and arc calcifications • Thickened cortex, endosteal scalloping Lymphoma • Moth-eaten lytic bone destruction • No periosteal new bone formation Aneurysmal Bone Cyst (ABC) • Can look similar to telangiectatic OGS • Purely lytic • No periosteal reaction Myositis Ossificans • Bone formation in periphery, zonal phenomenon o Surface OGS: Central bone formation • Cleft between osseous mass and cortex

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