BONE PATHOLOGY CASE STUDIES

CASE 2 - Malignant round cell tumor (Ewing's sarcoma)

Clinical History:

This is an 11 year old male who presents with right leg pain. The pain is worse at night and there is no mechanical pain. He has had decreased motion of the knee, secondary to pain. Radiographs demonstrate a lytic lesion in the diaphyseal region of the right fibula. (Slide 2.1) Additionally, a magnetic resonance imaging (MRI) scan show a soft tissue mass around the fibula. (Slide 2.2)
  1. What is the diagnosis?

    2. This is one of the so-called "round cell tumors" and is Ewing's sarcoma. The cells are small and primitive and round. I have no idea what the cell of origin is. These cells characteristically make lots of glycogen.

  2. In whom and at what sites is this lesion most common?

    3. There is slight male predominance. Ewing's sarcoma is seen mostly in children to young adults, with the pelvis and lower extremities accounting for most of the sites of origin. The diaphysis is usually involved.

  3. What are some other small round cell tumors of childhood?

    4. Histiocytoses (cousins of lymphoma) occur in bone in kids. Other round cell malignancies of childhood (not commonly involving bone) include medulloblastomas of brain and neuroblastomas of adrenal.