Bone Pathology Case Studies


CASE 6: Aneurysmal bone cyst


Clinical History:

An 18-year-old woman has noted pain and swelling of her right distal thigh for the past 2 months. The pain is associated with activity. She is a cheerleader and notices tenderness after performing acrobatics. She has no history of any trauma. Laboratory studies show serum calcium 8.9 mg/dL, phosphorus 3.3 mg/dL, alkaline phosphatase 133 U/L, albumin 4.9 g/dL, and total protein 6.8 g/dL. Radiographs are taken of the right knee region. A lesion is curretted.
  1. What is the diagnosis?

    This is an aneurysmal bone cyst (ABC). Radiographs show an expansile, eccentric lesion located in the metaphysis of the distal femur that is surrounded by a rim of reactive new bone as a host response.

  2. What is the major differential diagnosis?

    3. The major differential diagnosis for ABC is a giant cell tumor (GCT) of bone. However, a GCT occurs in the epiphysis, is more cellular, does not have periosteal reaction, occurs more often in adults, and has a tendency to recur after resection).

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

    4. ABC's have a female predominance and are more likely to occur in children and young adults. Vertebra, femur, and tibia are most often affected.

  4. Why should these lesions not be treated with radiation?

    5. There is a tendency for these lesions to undergo malignant transformation when radiated.