Question

What is the likely cause of a circumscribed osteosclerotic lesion in the tibial diaphysis in a 10 year old?

• A. Osteoid osteoma
• B. Ewing's sarcoma
• C. Bone secondaries
• D. Tuberculosis

Hint:

Think of a small dense nidus with a thick reactive sclerotic rim in a long bone shaft, with night pain relieved by aspirin.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
A 10 year old child has a well-defined, dense (sclerotic) lesion inside the shaft of the tibia. We need to pick the bone lesion that fits this exact picture: young age, diaphysis, sharply marked border, and increased bone density around it.

Step 2: Key Formula or Approach:
Match each option to its classic radiological look and age group. A benign, small, sharply outlined lesion surrounded by thick new bone points to osteoid osteoma. A ragged, poorly marked lesion eating into bone points to a malignant or infective cause.

Step 3: Detailed Explanation:
Osteoid osteoma is a small, benign, bone-forming tumor. It sits most often in the diaphysis of long bones such as the femur and tibia, and it is most common in the second decade of life, which fits a 10 year old. On X-ray it shows a small radiolucent nidus, usually under 1.5 to 2 cm, wrapped in a thick ring of dense reactive bone. This dense ring is exactly the "circumscribed osteosclerotic lesion" the question describes. The classic history is bone pain that gets worse at night and eases with aspirin or other NSAIDs.
Ewing's sarcoma also favors the diaphysis of long bones in children, but it looks very different on X-ray: a poorly defined, moth-eaten or permeative area of bone destruction, often with layered "onion-skin" periosteal new bone and a soft tissue mass. It is not a sharply marked sclerotic lesion.
Bone secondaries (metastases) are rare at age 10. Metastatic bone disease is mostly a disease of older adults with a known primary cancer such as breast, lung, prostate, or thyroid. Even the rare pediatric metastasis (for example from neuroblastoma) does not classically show as a small, sharply circumscribed sclerotic nidus.
Tuberculosis of bone usually causes a rarefying, destructive lesion (bone loss, not bone gain), often at the metaphysis or in the spine, with a ragged margin and surrounding soft tissue changes. It does not produce a small, dense, sharply outlined osteosclerotic spot.

Step 4: Final Answer:
The lesion that fits a small, sharply marked, sclerotic diaphyseal lesion in a 10 year old is osteoid osteoma.
\[ \boxed{\text{Osteoid osteoma}} \]