Bone and soft-tissue sarcomas — formative SAQs

SAQ 1 (10)

A fourteen-year-old boy presents with three months of deep aching pain in the distal right thigh, worse at night and unrelated to football. His mother now feels a firm swelling just above the knee. A plain radiograph shows a mixed lytic and sclerotic lesion in the distal femoral metaphysis with cortical destruction, perpendicular sunburst spicules and a triangular lifted periosteum. ^{[1] [3]}

a) Name the most likely diagnosis, and explain how each radiographic feature (the metaphyseal site, the mixed lytic and sclerotic matrix, the sunburst and the triangular periosteal reaction) supports it. (3 marks) ^[1]

b) State the local and distant staging investigations you would arrange, and justify the magnetic resonance imaging of the whole compartment and the computed tomography of the chest. (3 marks) ^[3]

c) A colleague offers to book the boy for an open excisional biopsy in the local theatre the next day. State the principle that governs the biopsy of a suspected sarcoma, the harm the unplanned biopsy causes, and where the biopsy should instead be performed. (2 marks) ^[1]

d) Outline the definitive treatment plan, naming the chemotherapy backbone, the timing of the surgery relative to the chemotherapy, and the role of the histologic response. (2 marks) ^[1][2]