Dedifferentiated parosteal osteosarcoma of the femur with aneuploidy and lung metastases

In this report, the pathologic findings and the results of cellular DNA measurements of a tumor that on first presentation seemed to be a classical parosteal osteosarcoma are described. After resection 8 months later, part of the tumor appeared to display highly malignant features. DNA flow cytometry of this part of the tumor showed an aneuploid cell population. The agressive nature of the tumor was confirmed by the development of lung metastases approximately 1 year after resection of the primary tumor.