ARRS Case of the Week- Jan 8, 2018

MUSCULOSKELETAL IMAGING: Metabolic/Hematologic

Case Author: Daniel E. Wessell, MD, PhD, Mallinckrodt Institute of Radiology at Washington University in Saint Louis

History

76-year-old man with recent 80-pound (36 kg) weight loss. CT has been performed, and the next best step based on the CT findings must be determined.

Imaging Findings

Axial pelvic CT images at the level of the femoral necks and windowed for bone (A) and soft tissue (B) show a lucent focus (arrow) in the right femoral neck.

Biopsy of the femoral neck lesion
MRI of the pelvis with contrast administration
No additional workup required
PET/CT
Serum and urine electrophoresis
^99mTc whole-body bone scan

Diagnosis

No additional workup required

Teaching Points

Osteoporosis is by far the most frequently encountered metabolic bone disease. Osteoporosis can have an aggressive appearance on radiographs, occasionally mimicking multiple myeloma and lytic metastasis. Macroscopic fat in a bone lesion is an excellent sign of benignity. Aggressive and nonspecific lytic lesions require further workup, which can include laboratory evaluation, MRI, ^99mTc whole-body bone scan, or even biopsy. MRI findings can narrow the differential diagnosis of an aggressive lesion, but the primary role of MRI is lesion staging. A whole-body bone scan before biopsy may depict an additional site of involvement that may be more safely biopsied.

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