| January 2005 Case of the Month |
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Compiled By: William Passodelis, MD
History: 48 year old male with mass at right distal femur and occasional pain.
Findings: At the distal one third of the femoral metaphysis, thickening and prominence of the periosteum is seen with areas that are both smooth and mildly irregular, and consistent with new bone formation. This is seen medially and has maximum mediolateral dimension of approximately 2cm. and maximum dimension longitudinally of approximately 9.5cm.. This extends to the medial femoral condyle. The medial to lateral measurement includes adjacent soft tissue component. This soft tissue component enhances following gadolinium administration.
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On the axial images, evidence of soft tissue component abutting the vastus medialis musculature in its lateral aspect is present and there is evidence of enhancement, not only of the soft tissue component, but extending into the vastus medialis muscle laterally as well. Soft tissue component extends in a circumferential pattern around the right femur and there is evidence for involvement of the medial aspect of the vastus intermedius muscle anteriorly as well, with minimal enhancement of the inferomedial aspect. Posteriorly, soft tissue component extends circumferentially to the semimembranosus muscle, however no enhancement is seen within the anterior aspect of the semimembranosus muscle.
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The marrow space of the right femur along this area is well preserved.
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The femoral vein is adjacent to an inferoposterior portion of the vastus medialis which shows mild enhancement following gadolinium; however, there does appear to be a fascial plane between the vastus medialis muscle and the femoral vein. No evidence of involvement of the femoral artery is seen. The sciatic nerve is at least 1cm distant, in its closest approach posteriorly, to the circumferential soft tissue component of the distal right femur.
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Discussion: Differential diagnosis for this case includes periosteal osteosarcoma, parosteal osteosarcoma, and possibly remote trauma and chronic sequelae of periosteal hemorrhage. We advised thin section C.T. for further evaluation of the cortex.
Osteogenic Sarcoma is a primary malignant tumor of bone. There are as many as twelve types of osteosarcoma, each having distinctive features, however in all types osteioid and bone matrix are formed by malignant cells.
TYPES:
Conventional Osteosarcoma;
most frequent
highest incidence in second decade, males slightly greater than females
predilection for knee, distal femur and proximal tibia
presentation is bone pain with occasional soft tissue mass and swelling.
possible pathologic fracture
radiologic features include medullary and cortical bone destruction,
aggressive periosteal reaction
soft tissue mass
tumor bone in destructive bone lesion, soft tissue mass, or both
Low Grade Osteosarcoma
rare
older patients
better prognosis
radiographically indistinguishable from conventional type
Telangiectatic
very aggressive
second and third decades predominate
male two times female occurrence
increased vascularity and large cystic spaces filled with blood
resulting in atypical radiographic characteristics
osteolysis and destruction, little sclerosis
soft tissue mass may be seen
Multicentric
rare
seen in children
multiple simultaneous foci, usually symmetric ( tip off against metastatic disease)
Parosteal
low grade
older patients
predilection for posterior distal femur
mass attatched to cortical bone surface
Periosteal
intermediate grade
usually diaphyseal
medullary sparing
Secondary Osteosarcoma
older population
can be seen as complication of Paget’s disease
DIFFERENTIAL DIAGNOSIS:
Ewings Sarcoma Osteomyelitis ( no bone formation, clinical information helpful)
Chondrosarcoma Lymphoma (no periosteal new bone)
Aneurysmal Bone Cyst (for Telangiectatic)
Myositis Ossificans (for Parosteal)
IMAGING:
Radiographs detect bone destruction and periosteal reaction
sunburst destruction and Codman’s triangle
MRI determines extent of disease within bone marrow and soft tissues
and relationship to vessels and nerves
T1 findings- low signal mineralized tumor low to intermediate signal soft tissue mass
T2 findings- low signal mineralized tumor high signal non mineralized tumor and soft tissue mass
STIR- helpful to detect skip lesions and multicentricity
Bone Scan- to check for possible skip lesions, multicentricity, metastatic disease
PET Scan- helpful to evaluate for recurrence.
TREATMENT: Surgical resection with wide margins. Adjuvant and neo-adjuvant chemotherapy. Amputation is often necessary. 4 to 5 year disease free overall survival rate in patients with NO demonstrable metastatic disease is approximately 80 % . |
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References:
Stoller MD, FACR, David W. et al. Diagnostic Imaging: Orthopaedics, Amirsys Inc. 2004 pgs 8:14-8:17
Greenspan MD, Adam Orthopedic Radiology, A Practical Approach, J.B.Lippincott Co. 1988 pgs16.2-16.9
Isselbacher AB,MD, Kurt J., Braunwald AB,MD,ScD, Eugene, Wilson MD, Jean, Martin MD, PhD, FRCP, MA, Joseph B., Fauci MD, Anthony S., Kasper MD, Dennis L., et al Harrison’s Principles of Internal Medicine, McGraw Hill 1994 pgs 2196-2197
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