**Core Concept**
The patient is presenting with signs and symptoms suggestive of a bone tumor, specifically a benign bone tumor known as an osteosarcoma or Ewing's sarcoma. The laminated periosteal reaction seen on X-ray is a characteristic feature of these tumors.

**Why the Correct Answer is Right**
The laminated periosteal reaction is a result of the bone's attempt to repair itself after the tumor's growth has disrupted the normal bone architecture. This reaction leads to the formation of a new layer of bone on the surface of the original bone, which appears as a layered or lamellated appearance on X-ray. The correct next line of investigation would be to obtain a biopsy sample of the affected bone tissue to confirm the diagnosis and rule out other potential causes of the patient's symptoms.

**Why Each Wrong Option is Incorrect**
* **Option A:** Imaging studies such as MRI or CT scans may provide additional information about the tumor's size and location, but they are not the next line of investigation.
* **Option B:** Blood tests such as ESR may be used to monitor the patient's response to treatment, but they are not useful for making a definitive diagnosis.
* **Option C:** A bone scan may be used to identify areas of abnormal bone metabolism, but it is not specific enough to confirm the diagnosis of a bone tumor.

**Clinical Pearl / High-Yield Fact**
When interpreting X-rays of the musculoskeletal system, it's essential to be aware of the characteristic signs of bone tumors, such as the laminated periosteal reaction. This can help narrow down the differential diagnosis and guide further investigation.

**Correct Answer:** D.