Primary reticulum-cell sarcoma of bone is a malignant tumor histologically indistinguishable from reticulum-cell sarcoma arising in other regions of the body. It originates at a single site in bone and, when metastasis occurs, it is usually by way of the lymphatics. Pain and swelling are the chief symptoms, and characteristically there is lack of constitutional reaction. The prognosis is relatively good, the five-year survival rate approaching 50 per cent following operation or proper irradiation. The importance of distinguishing between this tumor and other similar, but more malignant, conditions, such as osteogenic sarcoma and Ewing's tumor, is apparent. Several articles make mention of the roentgen findings in primary reticulum-cell sarcoma of bone, but the only paper in the English or American literature devoted specifically to evaluation of the roentgenologic appearance is that of Sherman and Snyder (1), whose study was based on a review of 17 cases. It seemed, therefore, that further study of this p...