What percent of giant cell tumor of bone are malignant ?
**Core Concept**
Giant cell tumors of bone (GCTs) are relatively rare, benign neoplasms primarily affecting the epiphyses of long bones. They are characterized by the presence of osteoclast-like giant cells and a mononuclear stromal component.
**Why the Correct Answer is Right**
The majority of GCTs are indeed benign, but a small percentage can exhibit malignant behavior. The exact percentage of malignant GCTs is around 5-10%. These malignant lesions are more aggressive and may exhibit features such as increased cellularity, pleomorphism, and mitotic activity. The malignant transformation is thought to arise from the mononuclear stromal cells, which may undergo genetic mutations leading to uncontrolled growth.
**Why Each Wrong Option is Incorrect**
**Option A:** 1% - This is too low, as the actual percentage of malignant GCTs is higher.
**Option B:** 20% - This is too high, as most GCTs remain benign.
**Option C:** 50% - This is significantly higher than the actual percentage and would make GCTs more common than benign bone tumors.
**Clinical Pearl / High-Yield Fact**
Malignant GCTs are more common in older patients and may exhibit a higher recurrence rate after surgical excision. It is essential to differentiate malignant GCTs from other aggressive bone tumors, such as osteosarcoma or chondrosarcoma.
**Correct Answer:** C. 5-10%