Commonest cause of skeletal metastasis is
**Core Concept**
The question is testing knowledge on the most common cause of skeletal metastasis, a type of cancer spread to the bones. Skeletal metastasis is a significant complication of various cancers, leading to bone pain, fractures, and other complications.
**Why the Correct Answer is Right**
The correct answer is **Prostate Cancer**. Prostate cancer is the most common cause of skeletal metastasis, accounting for approximately 70% of all skeletal metastases. This is due to the fact that prostate cancer cells have a high affinity for the bone microenvironment, where they can proliferate and cause bone destruction. The bone metastases of prostate cancer are characterized by osteoblastic lesions, which are areas of abnormal bone growth and density. The prostate cancer cells secrete factors that stimulate osteoblasts, leading to the formation of these lesions.
**Why Each Wrong Option is Incorrect**
**Option A:** Lung cancer is a common cause of skeletal metastasis, but it is not the most common. Lung cancer metastases to the bone are typically osteolytic, meaning they cause bone destruction rather than abnormal bone growth.
**Option B:** Breast cancer is another common cause of skeletal metastasis, but it is not the most common. Breast cancer metastases to the bone are typically osteolytic, and they often occur in the axial skeleton.
**Option C:** Renal cell carcinoma is a rare cause of skeletal metastasis compared to prostate cancer. Renal cell carcinoma metastases to the bone are typically osteolytic.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that prostate cancer is a leading cause of skeletal metastasis, and it's crucial to consider this diagnosis in patients with bone pain or other symptoms suggestive of metastatic disease.
**Correct Answer: D. Prostate Cancer**