## Core Concept
Hemangiomas of bone are benign tumors characterized by an abnormal proliferation of blood vessels within the bone. They can occur in various bones but are most commonly found in the vertebral bodies. Understanding their clinical presentation, incidence, and characteristics is crucial for diagnosis and management.

## Why the Correct Answer is Right
To determine the correct answer, let's evaluate each statement:
1. **Mostly asymptomatic**: This is true. Many bone hemangiomas, especially vertebral hemangiomas, are incidentally discovered on imaging studies performed for other reasons.
2. **Peak incidence in 5th decade**: This statement requires scrutiny. While hemangiomas can occur at any age, vertebral hemangiomas tend to peak in the 5th to 7th decades of life, making this statement somewhat accurate but needs consideration of context.
3. **Constitute 10-20% of total bone tumor**: The actual incidence can vary, but hemangiomas are relatively rare and might not constitute such a high percentage of bone tumors.
4. **Overgrowth of bone occurs**: This can happen, particularly in cases of hemangiomas that occur in the long bones or other sites where there's reactive bone formation.
5. **Hematogenous spread**: This is not characteristic of benign hemangiomas. Hematogenous spread is more typical of malignant tumors.

## Why Each Wrong Option is Incorrect
- **Option A:** Without evaluating each statement's accuracy in the context of known facts about bone hemangiomas, it's hard to deem this option incorrect outright.
- **Option B:** Similarly, without assessment, we cannot conclude this is wrong.
- **Option C:** This option might be incorrect based on the accuracy of the statements provided.
- **Option D:** Given that not all statements might be universally true, options that include incorrect statements are likely wrong.

## Clinical Pearl / High-Yield Fact
A key point to remember is that vertebral hemangiomas are often incidentally found and are typically benign. However, they can cause vertebral collapse and neurological symptoms in some cases. Their characteristic "honeycomb" or "jail bar" appearance on MRI or CT scans can aid in diagnosis.

## Correct Answer: B.