A 14-year-old boy presents with a 3-month history of progressive pain and swelling around his left knee. The pain is dull, constant, and often wakes him at night. His parents report that he has developed a limp and is unable to participate in sports. He has also experienced some weight loss and fatigue, though there has been no history of fever or night sweats.
On physical examination, there is a firm, tender swelling over the distal femur measuring approximately 6 cm. The swelling is immobile and associated with warmth and restriction of knee movement. The overlying skin appears stretched but intact, with no redness or ulceration. There is no palpable lymphadenopathy, and distal pulses are well felt.
Laboratory studies show the following results:
On physical examination, there is a firm, tender swelling over the distal femur measuring approximately 6 cm. The swelling is immobile and associated with warmth and restriction of knee movement. The overlying skin appears stretched but intact, with no redness or ulceration. There is no palpable lymphadenopathy, and distal pulses are well felt.
Laboratory studies show the following results: Hemoglobin 10.5 g/dL (12–16 g/dL - Mild anemia) ESR 40 mm/hr (<20 mm/hr - Elevated) CRP Normal (<10 mg/L - Normal) Alkaline Phosphatase (ALP) 700 U/L (<150 U/L- Markedly elevated) Lactate Dehydrogenase (LDH) 550 U/L (<250 U/L - Elevated)
A plain X-ray of the distal femur shows a destructive lesion in the metaphyseal region with mixed lytic and sclerotic changes. There is periosteal elevation forming a Codman’s triangle, and a characteristic “sunburst” appearance of periosteal reaction. Cortical breach with extension into adjacent soft tissue is also seen. MRI confirms a large heterogeneous metaphyseal mass extending into surrounding soft tissue, but without encasement of the neurovascular bundle. A staging CT of the chest reveals small pulmonary nodules suggestive of metastases.
A core needle biopsy demonstrates malignant spindle-shaped cells producing osteoid, confirming the diagnosis of osteogenic sarcoma (osteosarcoma) of the distal femur with pulmonary metastases