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.

[Illustration:  FIG. 148.—­Chondro-Sarcoma of Scapula in a man aet. 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.

Pathological fracture is more common in central tumours, and sometimes is the first sign that calls attention to the condition.  Consolidation rarely takes place, although there is often an attempt at union by the formation of cartilaginous callus.

[Illustration:  FIG. 149.—­Central Sarcoma of Lower End of Femur, invading the knee-joint.

(Museum of Royal College of Surgeons, Edinburgh.)]

[Illustration:  FIG. 150.—­Osseous Shell of Osteo-Sarcoma of Upper Third of Femur, after maceration.]

The soft parts over the tumour for a long time preserve their normal appearance; or they become oedematous, and the subcutaneous venous network is evident through the skin.  Elevation of the temperature over the tumour, which may amount to two degrees or more, is a point of diagnostic significance, as it suggests an inflammatory lesion.

The adjacent joint usually remains intact, although its movements may be impaired by the bulk of the tumour or by effusion into the cavity.

Enlargement of the neighbouring lymph glands does not necessarily imply that they have become infected with sarcoma for the enlargement may disappear after removal of the primary growth; actual infection of the glands, however, does sometimes occur, and in them the histological structure of the parent tumour is reproduced.

To obtain a reasonable prospect of cure, the diagnosis must be made at an early stage.  Great reliance is to be placed on information gained by examination with the X-rays.

[Illustration:  FIG. 151.—­Radiogram of Osteo-Sarcoma of Upper Third of Femur.]

X-ray Appearances.—­In periosteal tumours that do not ossify, there is merely erosion of bone, and the shadow is not unlike that given by caries; in ossifying tumours, the arrangement of the new bone on the surface is characteristic, and when it takes the form of spicules at right angles to the shaft, it is pathognomic.