**Core Concept**
Large intracytoplasmic glycogen storage is a characteristic histopathological feature of Ewing's sarcoma, a type of malignant bone tumor. This phenomenon is attributed to the high metabolic rate of Ewing's sarcoma cells, which rely heavily on glycolysis for energy production.

**Why the Correct Answer is Right**
Ewing's sarcoma is a primitive neuroectodermal tumor (PNET) that arises from the bone marrow. The cells of Ewing's sarcoma exhibit a high degree of cellular turnover, leading to an increased demand for energy. As a result, these cells accumulate large amounts of glycogen, which is stored within the cytoplasm. This histopathological feature is a key diagnostic criterion for Ewing's sarcoma, distinguishing it from other types of bone tumors.

**Why Each Wrong Option is Incorrect**
**Option A:** Osteosarcoma is a type of bone cancer that is characterized by the production of osteoid matrix by tumor cells. While osteosarcoma cells may exhibit some degree of cellular turnover, they do not typically accumulate large amounts of glycogen in their cytoplasm.

**Option B:** Mesenchymal chondrosarcoma is a rare type of bone cancer that arises from the cartilage-producing cells of the bone. This tumor type is characterized by a mixture of cartilaginous and mesenchymal elements, but it does not typically exhibit large intracytoplasmic glycogen storage.

**Option D:** Leiomyosarcoma is a type of smooth muscle tumor that can occur in various locations, including the soft tissues and bone. While leiomyosarcoma cells may exhibit some degree of cellular turnover, they do not typically accumulate large amounts of glycogen in their cytoplasm.

**Clinical Pearl / High-Yield Fact**
When confronted with a bone tumor that exhibits large intracytoplasmic glycogen storage, it is essential to consider Ewing's sarcoma in the differential diagnosis. This histopathological feature is a key diagnostic criterion for this malignancy, and it can help differentiate Ewing's sarcoma from other types of bone tumors.

**✓ Correct Answer: C. Ewing's sarcoma**