Presentation
Painless right distal radius mass.
Patient Data
There is a small focus of increased radiotracer activity at the distal right wrist with an area of central photopenia.
Lytic, expansile, well-defined lesion with internal septations in the distal radial metaphysis extending to the distal subchondral bone.
Cortical disruption along the medial aspect of the lesion, suggestive of a nondisplaced pathologic fracture.
Case Discussion
The doughnut sign on a bone scan refers to increased activity along the periphery of a lesion with minimal radiotracer activity within the center 1. The doughnut sign is non-specific for a variety of mass bone lesions 2.
Differentials mainly include aneurysmal bone cysts, giant cell tumor of the bone, simple bone cysts, and chondrosarcoma. Biopsy is needed for definitive diagnosis.
This patient's biopsy demonstrated giant cell tumor, consistent with the differential provided by the doughnut sign.
This case is submitted in collaboration with Dr. Raymond Sun, Dr. Omar Al Jammal, and Shriraj Susarla, Los Angeles County + University of Southern California (LAC+USC).
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