**Core Concept**
The case presents a lytic lesion with sclerotic margins in the mid tibia of a 10-year-old boy. This radiographic appearance is suggestive of a bone tumor with a mix of destructive and reactive bone formation. The key principle here is to identify the underlying bone tumor based on the given characteristics.

**Why the Correct Answer is Right**
The presence of a lytic lesion with sclerotic margins is characteristic of an osteosarcoma, particularly the telangiectatic variant. This variant is known for its aggressive behavior and high vascularity, which leads to a lytic appearance on X-rays. The sclerotic margins are a result of reactive bone formation in response to the tumor's growth. The telangiectatic osteosarcoma is a subtype of osteosarcoma that typically affects children and young adults.

**Why Each Wrong Option is Incorrect**
**Option A:** Ewing's sarcoma is another bone tumor that can present with a lytic lesion, but it typically has a more homogeneous appearance and lacks the sclerotic margins seen in osteosarcoma.

**Option B:** Osteoblastoma is a benign bone tumor that can present with a lytic lesion, but it typically has a more central location and is less aggressive than osteosarcoma.

**Option C:** Fibrous dysplasia is a benign bone disorder that can present with a lytic lesion, but it typically has a more ground-glass appearance and lacks the sclerotic margins seen in osteosarcoma.

**Clinical Pearl / High-Yield Fact**
Remember that osteosarcoma is the most common primary bone malignancy in children and young adults, and it often presents with a lytic lesion and sclerotic margins on X-rays. Telangiectatic osteosarcoma is a subtype that is particularly aggressive and requires prompt treatment.

**Correct Answer:** C. Fibrous dysplasia is a benign bone disorder that can present with a lytic lesion, but it typically has a more ground-glass appearance and lacks the sclerotic margins seen in osteosarcoma.