Sunray appearance on X – ray is seen in –
**Core Concept**
The sunray appearance on X-ray is a radiological finding associated with bone lesions that infiltrate the surrounding soft tissues and cortex, often indicating aggressive bone destruction. This phenomenon is characterized by radiating streaks of bone destruction extending from the center of the lesion towards the periphery.
**Why the Correct Answer is Right**
The sunray appearance is typically seen in osteosarcoma, a malignant bone tumor that exhibits aggressive bone destruction and periosteal reaction. The periosteum, a layer of connective tissue surrounding the bone, reacts to the tumor by forming a new bone layer, which can give the appearance of radiating streaks or "sunrays" on X-ray. This is due to the periosteal reaction, a process where the periosteum attempts to contain the expanding tumor by laying down new bone.
**Why Each Wrong Option is Incorrect**
**Option A:** Fibrous dysplasia can cause bone deformities and sclerosis, but it does not typically exhibit a sunray appearance on X-ray.
**Option B:** Osteomyelitis can cause bone destruction, but the sunray appearance is not a characteristic feature of this condition.
**Option C:** Paget's disease can cause bone deformities and sclerosis, but it typically exhibits a "cotton wool" appearance on X-ray rather than a sunray appearance.
**Clinical Pearl / High-Yield Fact**
The sunray appearance is a classic radiological sign of osteosarcoma, a malignant bone tumor that requires prompt diagnosis and treatment.
**Correct Answer: C. Osteosarcoma.