Cortical Desmoid - MSK Radiology
Imaging Findings:
• Circumscribed, small cortically based Tl -hypointense and T 2-hyperintense lesion of the posteromedial femoral metaphysis. This lesion displays cortical irregularity with no other aggressive features.
• Peripheral T2-hypointense sclerosis surrounding the lesion.
• The lesion is at the attachment site of the medial head gastrocnemius tendon.
Case description:
• "Distal femoral cortical irregularity" and "Avulsive cortical irregularity" are also appropriate and more accurate terms.
• "Desmoid" is a misnomer as this does NOT histologically correlate to a desmoid tumor.
• Most regard this entity as related to avulsive injury on a chronic basis, however, others consider this entity developmental in etiology. Typically in adolescents (10-15 years of age).
• T1-weighted low signal intensity and T2-weighted usually high-signal with peripheral low-signal sclerotic rim.
- Most have post-contrast enhancement.
- Bone scans CAN BE POSITIVE (don't get tricked!).
- Along the medial distal femur, 1-2 cm proximal to the physis.
- At the attachment of the medial head gastrocnemius or distal adductor magnus.
Differential diagnosis:
• Fibrous cortical defect: Cortically based benign lesion that is also peripherally sclerotic. Not in characteristic location and is preferentially subcortical in location.
• Osteosarcoma: Will have more aggressive radiographic features, however sometimes MR is ordered if the lesion is aggressive in appearance on radiograph. MR is able to distinguish between these entities based on location and lack of aggressive characteristics.
Dr. Donald von Borstel @DrvonBorstel
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