Primary Bone Neoplasms



Primary Bone Neoplasms


Todd M. Blodgett, MD

Alex Ryan, MD

Joanna Costello, MD





Key Facts


Terminology



  • Chondrosarcoma


  • Ewing sarcoma


  • Osteogenic sarcoma


Imaging Findings



  • PET/CT improves accuracy of identification and localization of invasive disease


  • Crucial for determining therapeutic strategy


  • FDG PET superior for detection of osseous lesions; CT for lung lesions


  • Low FDG uptake and metabolic activity in cartilaginous tissue


  • FDG uptake increases with more aggressive histologic tumor types


  • High pre-treatment SUV sensitive for higher grade tumor


  • PET/CT superior to CT alone for detection of minimal malignant residue


Top Differential Diagnoses



  • Bone Metastases


  • Other Bone Tumors


  • Acute Leukemia


  • Benign Bone Lesions


  • Fracture


  • Abscess/Osteomyelitis


  • Bone Infarction


  • Paget Disease


Diagnostic Checklist



  • Best time to perform FDG PET or PET/CT is prior to therapy to establish inherent FDG activity


  • Many sarcomas, including primary osseous sarcomas, may not be FDG avid






Graphic shows the typical appearance of a primary sarcoma of the femur image.






Coronal graphic shows the typical appearance of a mandibular osteosarcoma image.


TERMINOLOGY


Abbreviations and Synonyms



  • Chondrosarcoma


  • Ewing sarcoma


  • Osteogenic sarcoma, osteosarcoma, primary bone sarcoma


Definitions



  • Chondrosarcoma



    • Primary malignant tumor of bone


    • Produces hyaline cartilage leading to abnormal cartilage &/or bone


  • Ewing sarcoma



    • Primary malignant tumor of bone


  • Osteosarcoma



    • Primary malignant tumor of bone


    • Contains osteoid with osteoblastic differentiation


IMAGING FINDINGS


General Features



  • Best diagnostic clue



    • Chondrosarcoma



      • Mass with variable chondroid matrix


      • May have cortical disruption &/or soft tissue extension


      • FDG uptake tends to correlate with tumor grade


    • Ewing sarcoma



      • Permeative appearance ± extraosseous large soft tissue component adjacent to bone


    • Osteosarcoma



      • Heterogeneous metaphyseal mass


      • Increased FDG uptake with high grade osteosarcoma


      • May have characteristic starburst appearance


  • Location



    • Chondrosarcoma



      • Most common areas: Pelvis, femur, and humerus


      • Mostly in proximal aspect of long bones


      • Peripheral, periosteal, or central intraosseous locations


    • Ewing sarcoma



      • Most common in metaphysis or diaphysis of long bones


      • May arise in any bone


    • Osteosarcoma




      • Metaphyseal long bone


      • Distal femur


  • Size: Variable


  • Morphology



    • Ewing sarcoma



      • Obscured margins


      • Aggressive periosteal invasion


    • Osteosarcoma



      • Bone mass with destruction of bone elements


      • Cortical expansion


      • Large zone of transition


    • Chondrosarcoma



      • Endosteal scalloping


      • May have cortical destruction


      • Typically associated with a large soft tissue mass


Imaging Recommendations



  • Best imaging tool



    • FDG PET and PET/CT may be useful for staging, restaging, and response to therapy



      • Both have current insurance coverage limitations


CT Findings



  • Chondrosarcoma



    • Lytic mass with medullary cavity expansion


    • Variable amounts of calcification and chondroid matrix


    • Often have cortical thickening


    • ± Soft tissue mass


    • ± Endosteal scalloping


  • Ewing sarcoma



    • Commonly involves long bones (metaphysis or diaphysis)


    • Intramedullary mass ± involvement of the cortex



      • Permeative/“moth-eaten” appearance


      • Heterogeneous contrast enhancement


    • Periosteal reaction often described as “sunburst”



      • Large zone of transition


    • Soft tissue mass frequently present


    • Frequently metastasizes to lung, bone, and marrow


  • Osteosarcoma



    • Intramedullary mass


    • “Moth-eaten” appearance of osseous destruction


    • Indistinct borders


    • Wide zone of transition


    • Cortical break through


    • Most common in distal femur


    • Sunburst pattern of periosteal reaction


    • May have contrast enhancement


Nuclear Medicine Findings



  • Initial diagnosis



    • High grade tumors typically have intense FDG activity


    • FDG PET is sensitive for osteosarcoma and Ewing sarcoma


    • Chondrosarcoma shown to have low FDG uptake (average SUV of 4.5)


    • Histologic grade correlates well with SUV between high and low grade bone sarcomas


  • Staging



    • PET/CT improves accuracy of identification and localization of invasive disease



      • Crucial for determining approach to therapy


      • Invasion of adjacent structures can be determined


      • FDG PET superior for detection of osseous lesions


      • Useful for estimating percentage of tumor necrosis


      • PET/CT may offer additional biopsy localization information


      • CT more sensitive for lung lesions


    • Ewing sarcoma



      • Tend to be FDG avid


      • Small study reported overall sensitivity 96% and specificity 78%


      • PET/CT more sensitive than bone scan for osseous metastases


      • Degree of FDG uptake indicates disease stage and may have prognostic value


    • Chondrosarcoma



      • Low FDG uptake and metabolic activity in cartilaginous tissue


      • FDG uptake increases with more aggressive histologic tumor types



      • Cannot differentiate grade I chondrosarcoma from benign cartilage tumors


      • High pre-treatment SUV sensitive for higher grade tumor


      • High sensitivity for high grade mets


      • SUV may be as accurate as tumor grade for prognosis of overall survival


  • Restaging



    • PET/CT superior to CT alone for



      • Detection of minimal malignant residue


      • Distinction between vital and necrotic tumor regions


      • Improved detection and localization of recurrence in patients with implanted orthopedic devices


  • Response to therapy

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Sep 22, 2016 | Posted by in MAGNETIC RESONANCE IMAGING | Comments Off on Primary Bone Neoplasms

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