## Location and Radiographic Features of Giant Cell Tumor **Key Point:** Giant cell tumor (GCT) of bone is a benign but locally aggressive tumor with a characteristic epiphyseal-metaphyseal location, typically occurring *after* physeal closure in skeletally mature patients. ### Typical Location - **Epiphyseal and metaphyseal region** — extends to the articular surface - Occurs in patients aged 20–40 years, after skeletal maturity - Most common sites: distal femur, proximal tibia, distal radius, proximal humerus - ~~Diaphyseal location~~ — this is INCORRECT and is the answer to this "EXCEPT" question ### Radiographic Appearance - **Soap-bubble or honeycomb pattern** — due to multiple locules separated by bony septa - Lytic (radiolucent) lesion - Well-defined but non-sclerotic margins - Extends to subarticular cortex ### MRI Findings - Heterogeneous signal intensity - **Hemosiderin deposition** — appears as low-signal foci on T2-weighted images - Caused by recurrent microhemorrhages within the tumor - Fluid-fluid levels may be present ### Histopathology Correlation - Numerous multinucleated giant cells (osteoclast-like) - Stromal mononuclear cells - Hemosiderin-laden macrophages - Occasional mitotic figures (does NOT indicate malignancy) **High-Yield:** The diaphyseal location is characteristic of other benign tumors (e.g., fibrous dysplasia, enchondroma) or malignant lesions, NOT GCT. GCT is pathognomonic for the epiphyseal-metaphyseal region in a skeletally mature patient. **Clinical Pearl:** A young adult with a lytic epiphyseal lesion extending to the articular surface = think GCT first. Diaphyseal location should prompt you to consider alternative diagnoses. [cite:Robbins 10e Ch 26]
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.