(1) The soft cellular tumours are composed mainly of spindle or round cells; they grow from the marrow of the spongy ends or from the periosteum of the long bones, the diploë of the skull, the pelvis, vertebræ, and jaws. As they grow they may cause little alteration in the contour of the bone, but they eat away its framework and replace it, so that the continuity of the bone is maintained only by tumour tissue, and pathological fracture is a frequent result. The small round-celled sarcomas are among the most malignant tumours of bone, growing with great rapidity, and at an early stage giving rise to secondary growths.
(2) The second group includes the fibro-, osteo-, and chondro-sarcomas, and combinations of these; in all of them fully formed tissues or attempts at fully formed tissues predominate over the cellular elements. They grow chiefly from the deeper layer of the periosteum, and at first form a projection on the surface, but later tend to surround the bone ([Fig. 150]), and to invade its interior, filling up the marrow spaces with a white, bone-like substance; in the flat bones of the skull they may traverse the diploë and erupt on the inner table. The tumour tissue next the shaft consists of a dense, white, homogeneous material, from which there radiate into the softer parts of the tumour, spicules, needles, and plates, often exhibiting a fan-like arrangement ([Fig. 151]). The peripheral portion consists of soft sarcomatous tissue, which invades the overlying soft parts. The articular cartilage long resists destruction. The ossifying sarcoma is met with most often in the femur and tibia, less frequently in the humerus, skull, pelvis, and jaws. In the long bones it may grow from the shaft, while the chondro-sarcoma more often originates at the extremities. Sometimes they are multiple, several tumours appearing simultaneously or one after another. Secondary growths are met with chiefly in the lungs, metastasis taking place by way of the veins.
Clinical Features.—Sarcoma is usually met with before the age of thirty, and is comparatively common in children. Males suffer oftener than females, in the proportion of two to one.
In periosteal sarcoma the presence of a swelling is usually the first symptom; the tumour is fusiform, firm, and regular in outline, and when it occurs near the end of a long bone the limb frequently assumes a characteristic “leg of mutton” shape ([Fig. 146]). The surface may be uniform or bossed, the consistence varies at different parts, and the swelling gradually tapers off along the shaft. On firm pressure, fine crepitation may be felt from crushing of the delicate framework of new bone.
Fig. 148.—Chondro-Sarcoma of Scapula in a man æt. 63; removal of the scapula was followed two years later by metastases and death.
In central sarcoma pain is the first symptom, and it is usually constant, dull, and aching; is not obviously increased by use of the limb, but is often worse at night. Swelling occurs late, and is due to expansion of the bone; it is fusiform or globular, and is at first densely hard, but in time there may be parchment-like or egg-shell crackling from yielding of the thin shell. The swelling may pulsate, and a bruit may be heard over it. In advanced cases it may be impossible to differentiate between a periosteal and a central tumour, either clinically or after the specimen has been laid open.
