1. Submitted by: Lindsey Fogle, MSIV Date Accepted: 25 August 2010
RAD 4001 Case Presentation
Faculty Reviewer: Sandra Oldham, M.D.
Principal Modality (1): Plain film
Principal Modality (2): MRI T1-weighted

2. 10yo boy with chronic leg pain
Plain film of left tibia and fibula

3. Findings Radiolucent nidus in the cortex of distal tibial diaphysis
Nidus surrounded by dense osteosclerosis
Axial cut of T1 post contrast image shows well demarcated, enhancing lesion
Plain film of left tibia and fibula
Axial T1-weighted MRI post contrast

4. Differential Diagnosis
Focal bone lesion
Increased bone density
Osteoblastic Metastases
Prostate, breast, lymphoma, carcinoid
Chronic Osteomyelitis
Paget’s disease
Avascular necrosis
Femor/humeral head or fx of scaphoid
Sickle Cell, Polycythemia, vasculitis, trauma, steroids/Cushing’s, Legg-Calve-Perthes dz
Bone neoplasm
Decreased bone density
Osteolytic Metastases
Renal, thyroid, lung, breast
Osteomyelitis
Acute or chronic
Multiple Myeloma
Bone cyst
Fracture

5. Differential Diagnosis
Benign bone tumors
Osteoid osteoma
Osteoblastoma
Osteochondroma
Osteofibrous dysplasia
Fibrous dysplasia
Enchondroma
20-50yo; M=F; bones of hands/feet
Giant cell tumor
20-40yo; F>M; epiphysis of distal femur/proximal tibia
Malignant bone tumors
Osteosarcoma
Chondrosarcoma
30-60yo; M>F; pelvic bones/proximal femur
Ewing's sarcoma
Bone cysts
Typically appear lytic, expansile, with thin surrounding cortical bone

6. Osteochondroma M>F; 10-30yo
Hamartomatous lesion resulting from a defect in the growth plate on the metaphyseal side; direct communication with medullary canal; always points away from joint of origin
Pedunculated (distal femur) or sessile (proximal humerus)
Familial form (Hereditary Multiple Exostosis) is AD with diffuse involvement
Findings: cartilaginous cap at bony base is required for diagnosis
Surgery if symptomatic only; most are assymptomatic

7. Osteofibrous Dysplasia
M>F; ≤ 10yo
Usually asymptomatic, but can cause anterior bowing
Suspected to be a hamartomatous process that involutes
Almost exclusively in the diaphysis of the tibia, but can occur in the fibula or bilaterally
Findings: lytic lesions surrounded by sclerosis -> “soap bubble appearance”
Treat large or symptomatic lesions with curettage and bone grafting
Fibrous dysplasia: F>M; dx typically before 30yo; Inability to produce mature lamellar bone; can be monostotic/polyostotic or polyostotic with endocrine abnormalities (McCune-Albright syndrome); also takes soap bubble appearance -> need histology to differentiate; treatment is same

8. Osteosarcoma (classic)
M>F; 10-25yo
Second most common primary malignancy of bone after Multiple Myeloma (20% of all primary bone malignancies)
Risk factors include Paget’s disease, Familial retinoblastoma, and radiation
Most in metaphysis of distal femur or proximal tibia; can also be in the proximal humerus
Aggressive, can metastasize to lungs
Findings: Lytic lesion that permeates giving “sunburst” appearance-> breakthrough of periostium results in “Codman triangle”
MRI indicated for staging and anatomic data for surgery
Treat with chemotherapy and surgery

9. Ewing’s Sarcoma M>F; 5-25yo Malignant bone lesion
Translocation abnormality involving chomosomes 11 and 22 in 90% of cases
Pelvis is most common location, but also seen in femur, tibia, humerus, and scapula
Typically in diaphyseal-metaphyseal region
Findings: central lytic lesion with extending destruction of cortex; takes “onionskinning” appearance from periosteal reaction
Can resemble osteomyelitis because of high grade nature, necrosis and liquefaction that occur, mistaking it for pus
Radiosensitive tumor, but current treatment also involves surgery

10. Osteoid Osteoma Epidemiology Pathology Clinical Presentation
10% of benign bone tumors; most common of the benign tumors
M>F; 5-30yo with peak incidence in 2nd decade
Most commonly in proximal femur, but also occurs in spine or tibial diaphysis
Pathology
Osteoid forming neoplasm <1cm in diameter of benign woven bone in the nidus
Nidus contains numerous osteoblasts and osteoclasts in vascular fibrous stroma
Note: Osteoblastomas are large Osteoid Osteomas with preference for the posterior spine
Clinical Presentation
Usually assymptomatic
Night pain or dull, aching pain that is progressive
Tenderness over lesion
Classification for all benign tumors
Stage 1 – latent; generally asymptomatic; usually resolve on their own
Stage 2 – active; less well demarcated; require more aggressive treatment
Stage 3 – aggressive lesions; extensive destruction; requires wide en bloc resection
Treatment
Pain relieved by NSAIDs
High concentration of prostaglandins in nidus
50% will “burn out” over time
If NSAIDs fail..
CT guided radiofrequency ablation (IR)
Surgical removal (Ortho)

11. Typical findings of Osteoid Osteoma
Radiolucent nidus on plain film
Measures up to 1cm in diameter
Nidus surrounded by dense, reactive osteosclerosis if a cortical lesion; creates an extending fusiform bulge
Less sclerosis noted with more central lesions
Inflammatory synovitis can result if adjacent to or in a joint
Technetium bone scan is always positive
CT is helpful for anatomic data in preparing for surgery

12. CT-guided Radiofrequency Ablation (RFA)
Axial CT without contrast images of left distal tibia and fibula

13. Pre- and Post-RFA Pre-treatment Post-treatment
Axial T1 weighted MRI post contrast images of left distal tibia and fibula

14. References
Herring, William. "Chapter 21: Recognizing Abnormalities of Bone Density." Learning Radiology: Recognizing the Basics. Philadelphia: Mosby Elsevier, Print.
Goljan, Edward F. "Chaprter 23: Musculoskeletal Disorders." Pathology. Philadelphia, PA: Mosby Elsevier, Print.
Polousky John D, Eilert Robert E, "Chapter 24. Orthopedics" (Chapter). Hay WW, Jr., Levin MJ, Sondheimer JM, Deterding RR: CURRENT Diagnosis & Treatment: Pediatrics, 19e:
Randall R. L, Hoang Bang H, "Chapter 6. Musculoskeletal Oncology" (Chapter). Skinner HB: CURRENT Diagnosis & Treatment in Orthopedics, 4e:
Srinivasan Ramesh C, Tolhurst Stephen, Vanderhave Kelly L, "Chapter 40. Orthopedic Surgery" (Chapter). Doherty GM: CURRENT Diagnosis & Treatment: Surgery, 13e:
Zeiger Roni F, McGraw-Hill's Diagnosaurus 2.0:
Special thank you to M.D. Anderson Cancer Center for patient’s images.