Clinical History:
- An 18-year-old man had a six-month history of progressive pain in his left distal thigh. He had some moderate swelling about his knee for the past month. He noted that the pain was worse at night. He did not have pain with ambulation. On physical examination he was afebrile. He had slightly decreased range of motion of his left knee due to swelling in the lower left thigh. There was no erythema, warmth, or tenderness. No external signs of trauma were noted. There were no other abnormal findings. Laboratory studies showed Hgb 14.8 g/dL, Hct 44.5%, serum calcium 9.1 mg/dL, phosphorus 3.5 mg/dL, alkaline phosphatase 222 U/L, total protein 7.1 g/dL, and albumin 5.3 g/dL. Radiographs demonstrated a lesion of the distal femur.
- What is the diagnosis?
A typical osteosarcoma is present, arising in the metaphyseal region. The hard white areas seen grossly are areas of osteoid matrix microscopically. The tumor is composed of anaplastic spindle cells typical of a sarcoma, with prominent hyperchromatism, pleomorphism, and occasional mitoses. A large, bizarre mitotic figure is seen in image 1.8. Metastases from such a lesion would probably be hematogenously spread.
- In whom and at what sites is this lesion most common?
There is a slight male predominance, with peak incidence from teenage to young adulthood. The most common sites are in long bones, particularly around the knee.
- Can you name possible environmental causes for such a lesion?
An uncommon complication of radiation therapy is sarcoma. There are some radiation-induced osteosarcomas. Following the Chernobyl nuclear accident, Strontium-90 was released and got into soil, then into grass, was eaten by cows, and cows' milk was ingested by children who then have an increased risk for osteosarcoma. Remember, though, that bone trauma IS NOT a cause for sarcomas.
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