Which of the following imaging findings is most characteristic of giant cell tumor of bone on plain radiographs?

Explanation

## Giant Cell Tumor of Bone — Imaging Characteristics **Key Point:** Giant cell tumor (GCT) of bone is a benign but locally aggressive tumor with a pathognomonic location (epiphysis extending into metaphysis) and eccentric, lytic appearance with well-defined margins. ### Location and Radiological Features **High-Yield:** GCT occurs almost exclusively in the **epiphysis and extends into the metaphysis** after physeal closure in young adults (20–40 years). This epiphyseal location is virtually diagnostic. | Feature | Giant Cell Tumor | Osteosarcoma | Ewing Sarcoma | | --- | --- | --- | --- | | **Location** | Epiphysis → metaphysis | Metaphysis (around knee) | Diaphysis | | **Age** | 20–40 years | 10–25 years | 10–25 years | | **Margins** | Well-defined, eccentric | Ill-defined, aggressive | Ill-defined, aggressive | | **Periosteal reaction** | None or solid | Sunburst, Codman | Onion skin, lamellated | | **Internal pattern** | Lytic, homogeneous | Mixed lytic-sclerotic | Lytic, homogeneous | **Clinical Pearl:** The eccentric location in the epiphysis extending to metaphysis is so characteristic that it is sometimes called the "telltale" sign of GCT. This distinguishes it from other benign lesions that are typically metaphyseal or diaphyseal. **Mnemonic:** **EPIC** — **E**piphyseal location, **P**ost-physeal closure (20–40 yrs), **I**ncreases into metaphysis, **C**haracteristically eccentric.