During a tumor board discussion, an orthopedic surgeon reviews the imaging of 10 consecutive patients with histologically confirmed giant cell tumors of bone. When analyzing the distribution of lesions, which of the following represents the most common age group at presentation?

Explanation

## Most Common Age of Presentation for Giant Cell Tumor ### Epidemiological Profile **Key Point:** Giant cell tumor of bone presents most commonly in **skeletally mature patients aged 20–40 years**, with a peak incidence in the third and fourth decades of life. **High-Yield:** This age-at-presentation is a cardinal diagnostic clue: | Age Group | Frequency | Clinical Significance | |-----------|-----------|----------------------| | **20–40 years** | **Peak incidence (60–70%)** | **Most common presentation** | | 15–25 years | ~20–25% | Younger end of spectrum | | 40–60 years | ~10–15% | Less common | | <15 years | <5% | Rare (usually after physeal closure) | | >60 years | <5% | Uncommon | ### Critical Pathological Timing **Mnemonic — "GIANT = Growth After physeal closure":** Giant cell tumors arise *after* skeletal maturity is achieved. The tumor requires: 1. Closed growth plates (physeal closure) 2. Epimetaphyseal location accessibility 3. Mature skeletal environment This explains why giant cell tumors are virtually **never seen in children with open physes** and why they peak in young adults. ### Clinical Pearl The classic presentation is a **20–40-year-old patient** with a painless or mildly painful swelling around a major joint (especially the knee). The tumor typically: - Arises in the epimetaphysis *after* physeal closure - Extends to the subarticular cortex - Presents with a lytic, eccentric lesion on radiographs - Shows the characteristic "soap-bubble" or "honeycomb" pattern ### Differential Age Considerations - **Osteosarcoma:** typically 10–25 years (skeletally immature, during growth spurt) - **Ewing's sarcoma:** typically 10–20 years (diaphyseal, skeletally immature) - **Giant cell tumor:** typically 20–40 years (epimetaphyseal, skeletally mature) - **Metastatic disease:** typically >40 years **Warning:** A giant cell tumor presentation in a patient <15 years old or >60 years old should raise suspicion for alternative diagnoses or recurrent/malignant transformation. [cite:Rockwood & Green's Fractures in Adults Ch 32]