**Core Concept**
Rhabdomyosarcoma is a malignant tumor of skeletal muscle origin, accounting for a significant proportion of soft tissue sarcomas in children and young adults. It is a type of embryonal sarcoma, characterized by the abnormal proliferation of skeletal muscle cells.

**Why the Correct Answer is Right**
Rhabdomyosarcoma arises from the embryonal mesenchyme, where skeletal muscle cells differentiate. The tumor cells exhibit characteristics of immature skeletal muscle cells, such as the presence of rhabdomyoblasts and cross-striations under electron microscopy. Rhabdomyosarcoma is classified into three main subtypes: embryonal, alveolar, and pleomorphic, based on histological and cytogenetic features.

**Why Each Wrong Option is Incorrect**
* **Option A:** Leiomyosarcoma is a malignant tumor of smooth muscle origin, which is a distinct entity from skeletal muscle tumors.
* **Option B:** Osteosarcoma is a malignant tumor of bone origin, characterized by the production of osteoid matrix, and is not a type of skeletal muscle tumor.
* **Option C:** Neuroblastoma is a malignant tumor of neural crest origin, primarily affecting the sympathetic nervous system, and is not a type of skeletal muscle tumor.

**Clinical Pearl / High-Yield Fact**
Rhabdomyosarcoma often presents with a rapid onset of symptoms, including pain, swelling, and functional impairment of the affected limb or organ. Early diagnosis and treatment are crucial to improve prognosis and prevent metastasis.

**Correct Answer:** C.