Case 48
Presentation:
A 57-year-old male presents with left leg pain, and a whole-body planar bone scan was performed to evaluate his condition. What are the findings on the bone scan?
There is mild focal uptake in the medial aspect of the proximal left tibia. No other abnormal MDP uptake is observed elsewhere in the body.
A radiograph of the left leg was subsequently performed.
There is a lesion with heterogeneous, radiopacity eccentrically located in the left tibial metaphysis near the physis, with sclerotic rim, parallel to the axis of the bone.
What are the differential diagnoses based on the bone scan and X-ray findings?
Infection (OM)
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Trauma (Stress fracture/shin splint)
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Neoplasm: Benign Vs. Malignant
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Benign ( Fibrous dysplasia, aneurysmal bone cyst (donut sign), enchondroma, osteoma, bone island, NOF,OO)
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Malignant (Osteosarcoma)
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In this case, the bone scan and radiographic findings were suggestive of non-ossifying fibromas, which was subsequently confirmed by MRI.
Discussion:
Non-ossifying fibromas (NOFs) are benign, typically asymptomatic, and often found incidentally in adolescents and young adults.
NOFs typically progress through several phases as they mature and eventually heal. The phases include:
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Lytic (Active) Phase: The lesion is radiolucent, well-defined, and often lobulated, typically found in growing children and adolescents.
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Involutional Phase: The lesion begins to fill in with bone, showing increased sclerosis and reduced radiolucency.
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Burned-Out (Sclerotic) Phase: The lesion becomes fully ossified and radiopaque, indicating a healed, inactive
Bone scan appearance:
On a bone scan, an active non-ossifying fibroma (NOF) shows mild radiotracer uptake due to growth-related metabolic activity, while a burned-out NOF exhibits minimal to no uptake, reflecting its inactive state. This lower uptake helps distinguish NOFs from more aggressive lesions.
Plain radiography:
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Well-defined, eccentric lucent Lesions: They are often located in the metaphysis of long bones, such as the femur or tibia, and are eccentric (off-center) in position. The lesion center is typically radiolucent, as it does not contain bone, contrasting with the surrounding sclerotic rim.
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Cortical expansion with a thin sclerotic margin: The lesion may cause mild expansion of the bone, with a thin, well-defined sclerotic border surrounding it, indicating a non-aggressive process.
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Lobulated or multi-loculated appearance: The interior of the lesion often shows a lobulated or “bubbly” appearance, giving a multi-loculated pattern.
Treatment:
Non-ossifying fibromas (NOFs) are benign and usually require no treatment, often resolving spontaneously. Observation is typical, with surgery rarely needed unless the lesion is large or symptomatic. The prognosis is excellent, with most NOFs healing by adulthood and a low risk of recurrence or complications.
References:
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Hartmann, Wolfgang, Dorothee Harder, and Daniel Baumhoer. "Giant cell-rich tumors of bone." Surgical Pathology Clinics 14.4 (2021): 695-706.
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Goldin, A., et al. "The aetiology of the non-ossifying fibroma of the distal femur and its relationship to the surrounding soft tissues." Journal of Children's Orthopaedics 11.5 (2017): 373-379.
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Choi, Joon Hyuk, and Jae Y. Ro. "The 2020 WHO classification of tumors of bone: an updated review." Advances in anatomic pathology 28.3 (2021): 119-138.