**Core Concept**
Ewing's sarcoma is a malignant bone tumor characterized by rapid growth, pain, and a distinctive radiographic appearance. It often occurs in the pelvis, femur, or long bones, but can also arise in the mandible. The tumor is composed of primitive neuroectodermal cells that exhibit a characteristic "small round cell" morphology under microscopy.

**Why the Correct Answer is Right**
Ewing's sarcoma typically presents with a "Onion Skin" appearance on radiographs, caused by the formation of new subperiosteal bone in response to the tumor's aggressive growth. This radiographic feature, combined with the patient's symptoms of pain and lip paresthesia (numbness), suggests a diagnosis of Ewing's sarcoma. The elevated white blood cell count may indicate a systemic response to the tumor.

**Why Each Wrong Option is Incorrect**
**Option A:** Not relevant to Ewing's sarcoma, which is a primary bone tumor, not a metastatic disease.
**Option B:** Osteosarcoma is a different type of bone tumor that typically presents with a "sunburst" appearance on radiographs, not an "Onion Skin" pattern.
**Option C:** Chondrosarcoma is a cartilaginous tumor that often presents with a "rings and arcs" appearance on radiographs, not an "Onion Skin" pattern.
**Option D:** This option is not relevant to Ewing's sarcoma.

**Clinical Pearl / High-Yield Fact**
Ewing's sarcoma is a highly aggressive tumor that requires prompt diagnosis and treatment. The "Onion Skin" appearance on radiographs is a classic feature of this tumor, and should raise suspicion for Ewing's sarcoma in patients with a rapidly growing bone lesion.

**Correct Answer:** B.