more frequently in the male than in the female, and are most common in young adults. In childhood, the disease is rare.
Central spindle-celled tumors are next to the giant-celled, the most frequent. Myelogenic tumors of long bones, although they occur in one-third of the cases in the lower extremity of the femur, are found in the shaft relatively more frequent that are giant-celled tumors. They posses a higher degree of malignancy than do the giant-celled myeloid sarcoma, and occur as smooth or nodulated tumors, and are usually limited by a bony or fibrous capsule. Pain is nearly a constant symptom of these tumors. Spontaneous fracture or fracture from slight causes occurs in about one-half of the cases. Metastasis occurs in a large proportion while lymphatic involvement has never been observed.
Central round-celled sarcomas invade the shaft, and the epiphysis of the femur with equal frequency. The are the most rapidly growing tumor of bone, possessing a high degree of malignancy. They are usually vascular and rapidly undergo the retrograde changes common to all sarcoma, mucoid degeneration being the most common. Early in their development they break through the cortical layer of bone surrounding them, and quickly invade the neighboring soft tissues. Lymphatic involvement and generatization of the growth in distant organs occurs in a relatively short time. The growth of these tumors is constantly associated with great pain, rapid emaciation, cachexia and early death. Hemorrhages into the tumor, ulceration of the skin and spontaneous fracture occur more frequently than in any other variety of bone sarcoma.
Peripheral or periosteal sarcoma originate in the soft osteogenic layer of the periosteum, and in reality develop between the bone and periosteum. They are limited by the dense layer of the periosteum, which for some time offers sufficient resistance to prevent invasion of neighboring tissue. Histologically, they are either round or spindle-celled sarcoma. Giant-cells where found, probably reach the peripheral growth by extension through the bone from the medullary canal. Both spindle and round-celled periosteal growths exhibit a great tendency to ossification and calcification. According to Gross, 67 per cent. are osteoid sarcoma.
In general, peripheral sarcoma differs from central, in that they are not so common and that they are decidedly more malignant. Again they occur earlier in life and are more generally painful than the central tumors. Pulsation, which occurs in 20 per cent. of the central tumor, is seldom observed in peripheral tumors. Spindle and round-celled peripheral sarcoma usually involve the lower
