1. Primary reticulum-cell sarcoma of bone is an entity which may be differentiated from Ewing's sarcoma, histologically, with the aid of ordinary and special staining methods. The differentiation is important because of the different prognosis of each tumor.
2. The histochemical demonstration of glycogen in tumor cells of Ewing's sarcoma and its absence in reticulum-cell sarcoma of bone proved to be an easy, efficient method of differential diagnosis.
3. Appropriate fixatives and stains must be used to achieve uniform results.