Round cell lesions of bone

When you see a pemeative lesions with indistinct margins think "round cell lesions" and remember this list (in no particular order):
1) Infection
2) Langerhans cell histiocytosis
3) Lymphoma
4) Ewing's sarcoma
5) Metastases (neuroblastoma or small cell lung carcinoma [previously "oat cell carcinoma"])
6) Mesenchymal chondrosarcoma
7) Small cell osteosarcoma

The radiograph above is Ewing's sarcoma of the humerus.

Ken Yaw

Radiographic criteria to determine aggressiveness (which somewhat correlates with malignancy) in a bone lesion/tumor:
1) Size - big is worse than small
2) Margins - indistinct is worse than sharp/distinct
3) Cortical violation - penetration of cortex indicates more aggresive
4) Soft tissue mass - growth out of the bone into surrounding soft tissues indicates more aggressive

This radiograph shows an osteosarcoma of the proximal tibia.

Ken Yaw