A patient with Ewing's sarcoma. Histology shows small round cells. These cells are filled with which of the following -
Ewing sarcoma 

It is the second most bone sarcoma in children (after osteogenic sarcoma).
It is primary malignant small round cell tumor of bone.
It is derived from primitive neuroectoderm.
Age → 10-15 years, Sex → M > F
Usually arises in the diaphysis

Femur & Tibia → 2/3rd
Flat bones of pelvis → 3/3rd

Important microscopic features

Scant cytoplasm in tumor cells which is clear because it is rich in glycogen.
Homer - Wright rosettes.

Important Radiological features

Onion-skin periosteal reaction.
Sun-rays appearance (more common in osteogenic sarcoma).
Codman's triangle (It is also more common in osteogenic sarcoma).
Glycogen
Iron
Fat
Mucin