**Core Concept**
The rhabdomyosarcoma (RMS) is a type of malignant tumor that primarily affects children, arising from skeletal muscle progenitor cells. RMS is the most common soft tissue sarcoma in children, accounting for approximately 50% of all pediatric soft tissue sarcomas.

**Why the Correct Answer is Right**
The embryonal subtype of RMS is the most common form in children, typically presenting in the head and neck region (e.g., orbit, nasopharynx, larynx) or in the genitourinary tract. This subtype is characterized by its aggressive behavior and high mitotic rate, often leading to rapid tumor growth and metastasis. The embryonal subtype of RMS is known to express the PAX3-FOXO1 fusion gene, resulting from a chromosomal translocation involving the PAX3 and FOXO1 genes.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not specifically mention the embryonal subtype, which is the most common form of RMS in children.
**Option B:** This option is incorrect as it refers to a different type of soft tissue sarcoma, specifically alveolar RMS, which is less common in children than the embryonal subtype.
**Option C:** This option is incorrect as it is a characteristic of alveolar RMS, not embryonal RMS.

**Clinical Pearl / High-Yield Fact**
The PAX3-FOXO1 fusion gene is a key molecular marker for embryonal RMS, and its detection can aid in the diagnosis of this tumor type.

**Correct Answer: D.**