Commonest site of occurrence of chondrosarcoma is:
**Core Concept**
Chondrosarcoma is a type of malignant bone tumor that arises from cartilage-producing cells. It is the second most common primary malignant bone tumor after osteosarcoma, and it is characterized by its ability to invade surrounding tissues.
**Why the Correct Answer is Right**
Chondrosarcomas typically occur in the medullary cavity of long bones, particularly in the pelvis, femur, and humerus. They are often found in the metaphyseal region of the bone, where cartilage is actively producing new bone. The correct answer is the pelvis, as it is the most common site of occurrence for chondrosarcoma. This is likely due to the high concentration of cartilage in the pelvis, which provides a fertile ground for the development of this type of tumor.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because, while the femur is a common site for chondrosarcoma, it is not the most common site. The pelvis is more frequently affected.
**Option B:** This option is incorrect because, although the humerus can be affected by chondrosarcoma, it is not the most common site of occurrence. The pelvis is more frequently involved.
**Option C:** This option is incorrect because, although other bones can be affected by chondrosarcoma, the pelvis is the most common site of occurrence.
**Clinical Pearl / High-Yield Fact**
Chondrosarcomas are typically slow-growing and can cause pain and swelling in the affected area. They can also cause a palpable mass and can be associated with a pathologic fracture.
**Correct Answer: D. Pelvis.**