A boy from Sicily with knee pain

Case Identification

Case ID Number
Position within the bone
Periosteal reaction
Benign or Malignant

Clinical case information

Case presentation

A 12 year old boy from Sicily had a history of mild trauma to the right leg approximately one month prior to presentation. He presented with mild pain and a mass near the right knee.

Radiological findings:
AP and lateral radiographs of the distal femur, an axial and coronal MRI, and a CT scan image are shown. A radiograph and CT scan of the chest were negative (One abnormality or questionable nodule of uncertain significance was seen in the left lower lobe that we will ignore for the purposes of this exercise). A whole body bone scan showed abnormal uptake in the right distal femur but no other abnormality.
Laboratory results:
The alkaline phosphatase was 1174 (normal 240 -760).
Special Features of this Case:
1) What is the most likely diagnosis?

2) What is the stage of the tumor using the Enneking or Musculoskeletal Tumor Society's surgical staging system?

3a) This patient will undergo peroperative chemotherapy. How can the chemotherapy help determine his prognosis?

3b)What pre-operative blood tests have prognostic significance in this tumor?
Case Answer
Clinical Case Answer