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

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

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

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

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

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

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

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

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

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)

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

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

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

References Herring, William. "Chapter 21: Recognizing Abnormalities of Bone Density." Learning Radiology: Recognizing the Basics. Philadelphia: Mosby Elsevier, 2007. 217-30. Print. Goljan, Edward F. "Chaprter 23: Musculoskeletal Disorders." Pathology. Philadelphia, PA: Mosby Elsevier, 2007. 522-26. 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: http://www.accessmedicine.com/content.aspx?aID=3405856. Randall R. L, Hoang Bang H, "Chapter 6. Musculoskeletal Oncology" (Chapter). Skinner HB: CURRENT Diagnosis & Treatment in Orthopedics, 4e: http://www.accessmedicine.com/content.aspx?aID=2320059. Srinivasan Ramesh C, Tolhurst Stephen, Vanderhave Kelly L, "Chapter 40. Orthopedic Surgery" (Chapter). Doherty GM: CURRENT Diagnosis & Treatment: Surgery, 13e: http://www.accessmedicine.com/content.aspx?aID=5314010. Zeiger Roni F, McGraw-Hill's Diagnosaurus 2.0: http://www.accessmedicine.com/diag.aspx Special thank you to M.D. Anderson Cancer Center for patient’s images.