## **Core Concept**
The question pertains to the most common tumor occurring in infancy. Tumors in infancy are relatively rare but can include a variety of types, such as neuroblastoma, infantile hemangioma, and others. Understanding the common tumors in this age group is crucial for pediatric diagnosis and management.

## **Why the Correct Answer is Right**
The correct answer, **Infantile Hemangioma**, is the most common tumor of infancy. Infantile hemangiomas are benign tumors composed of proliferating blood vessels. They are characterized by an initial phase of rapid growth followed by involution. These tumors are highly vascular and can appear anywhere on the body. They are often present at birth or appear in the first few weeks of life.

## **Why Each Wrong Option is Incorrect**
- **Option A: Neuroblastoma** is a malignant tumor that originates from the neural crest cells. While it is a common extracranial solid tumor in children, it is not the most common tumor of infancy. Neuroblastoma can present at birth but is more commonly diagnosed later in infancy or early childhood.
- **Option B: Lymphangioma** is a benign tumor of the lymphatic system. It can occur in infancy but is not as common as infantile hemangioma.
- **Option C: Teratoma** is a type of tumor that can contain several different types of tissues. While teratomas can occur in infants, they are not the most common tumor in this age group.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that **infantile hemangiomas often involute spontaneously**, but they can cause significant morbidity due to their location, size, or complications such as bleeding or ulceration. Early recognition and management by a healthcare professional are crucial.

## **Correct Answer:** D. Infantile Hemangioma.