This 20-year-old has left hip pain when bearing weight and pushing hip out anteriorly.
Q1 – Which of the following is not in the differential diagnosis?
(a) Lymphoma / Hodgkin’s disease
(b) Aggressive giant cell tumor
(c) Non-aggressive giant cell tumor
(e) Myxoid clear cell chondrosarcoma
A1 – (a) Lymphoma / Hodgkin’s disease
Lymphoma / Hodgkin’s disease is an unlikely choice, even though this patient is age-appropriate. The differential diagnosis in this case is that of bone end lesions that are well-circumscribed. Lymphoma and Hodgkin’s disease are typically not bone end epiphyseal lesions. Multiple myeloma can occasionally involve such (bone ends or epiphyses) but would be highly unusual in a 20-year-old. Multiple myeloma is also not a lymphoproliferative abnormality but rather a disorder of plasma cells. The involvement and epicenter of the lesion in the femoral head narrows the differential diagnosis considerably, especially because it abuts the cortex.
Further, the lesion is expansile, especially along the inferior margin. Its hypointense rim is highlighted on the coronal series of images (images 1-3, pink arrows). The expansile character of the mass is appreciated along the inferior femoral head-neck junction (image 3, orange arrow). The absence of hypointensity within the lesion on PD SPAIR (image 3) mitigates against intralesional calicification or hemorrhage. Clear-cut cortical destruction is not discerned; however this is the type of case where a plain film would be of great value to assess cortical integrity and intralesional matrix.
The typical expansile bone end lesions that occur in this age group include:
(a) Chondroblastoma (usually patients are a little younger, but incites extensive edema)
(b) Chondroblastoma with clear cell chondrosarcomatous dedifferentiation (usually brighter on water-weighted sequences).
(c) Aggressive or non-aggressive giant cell tumor (often septated, may contain T2 hypointensities, average age 32).
(d) Aneurysmal bone cyst (usually brighter on T2 or PD fat-suppression, contains blood, delicate septations, even more expansile than this lesion).
(e) Telangiectatic osteogenic sarcoma with or without ABC (often larger or more expansile).
The axial images (images 4 and 5) suggest a “benign” lesion based on the sharp zone of transition.
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