The clinical features are those of a pulsating tumour of slow development, and as in true aneurysm, the pulsation and bruit disappear on compression of the main artery.  The origin of the tumour from bone may be revealed by the presence of egg-shell crackling, and by examination with the X-rays.

If the condition is believed to be innocent, the treatment is the same as for aneurysm—­preferably by ligation of the main artery; if malignant, it is the same as for sarcoma.

#Secondary Tumours of Bone.#—­These embrace two groups of new growth, those which give rise to secondary growths in the marrow of bones and those which spread to bone by direct continuity.

Metastatic Tumours.—­Excepting certain cancers which give rise to metastases by lymphatic permeation (Handley), the common metastases arising in the bone-marrow reach their destination through the blood-stream.

[Illustration:  FIG. 153.—­Epitheliomatous Ulcer of Leg with direct extension to Tibia.

(Lord Lister’s specimen.  Anatomical Museum, University of Edinburgh.)]

Secondary cancer is a comparatively common disease, and, as in metastases in other tissues, the secondary growths resemble the parent tumour.  The soft forms grow rapidly, and eat away the bone, without altering its shape or form.  In slowly growing forms there may be considerable formation of imperfectly formed bone, often deficient in lime salts; this condition may be widely diffused throughout the skeleton, and, as it is associated with softening and bending of the bones, it is known as cancerous osteomalacia.  Secondary cancer of bone is attended with pain, or it suddenly attracts notice by the occurrence of pathological fracture—­as, for example, in the shaft of the femur or humerus.  In the vertebrae, it is attended with a painful form of paraplegia, which may involve the lower or all four extremities.  On the other hand, the disease may show itself clinically as a tumour of bone, which may attain a considerable size, and may be mistaken for a sarcoma, unless the existence of the primary cancer is discovered.

The cancers most liable to give rise to metastasis in bone are those of the breast, liver, uterus, prostate, colon, and rectum; hyper-nephroma of the kidney may also give rise to metastases in bone.

Secondary tumours derived from the thyreoid gland require special mention, because they are peculiar in that neither the primary growth in the thyreoid nor the secondary growth in the bones is necessarily malignant.  They are therefore amenable to operative treatment.

Secondary sarcoma, whether derived from a primary growth in the bone or in the soft parts, is much rarer than secondary cancer.  Its removal by operation is usually contra-indicated, but we have known of cases terminating fatally in which the section revealed only one metastasis, the removal of which would have benefited the patient.