尤文氏肉瘤。这种原发性骨肿瘤主要见于儿童与青少年的长骨骨干，稍多见于男性。可见不规则的从灰色到红色再到棕色的肿瘤块正穿透皮质。最右侧可见正常的黄骨髓。
This is Ewing's sarcoma. This primary bone tumor mainly occurs in the diaphysis of long bones of children and young adults. There is a slight male predominance. As seen here, the irregular tan to red to brown tumor mass is breaking through the cortex. More normal fatty marrow is seen at the far right.