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 vertebræ, 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.
In all of these conditions, examination of the bones with the X-rays gives valuable information and often disclose unsuspected metastases.
Cancer of Bone resulting from Direct Extension from Soft Parts.—In this group there are also two clinical types. The first is met with in relation to epithelioma of a mucous surface—for example, the palate, tongue, gums, antrum, frontal sinus, auditory meatus, or middle ear. They will be described under these special regions.
The second type is met with in relation to epithelioma occurring in a sinus, the sequel of suppurative osteomyelitis, compound fracture, or tuberculous disease. The patient has usually had a discharging sinus for a great number of years: we have known it to last as many as fifty. The epithelioma originates at the skin orifice of the sinus, and spreads to the bone and into its interior, where the progress of the cancer is resisted by dense bone, which obliterates the medullary canal. Although its progress is slow, the infiltration of the bone is usually more extensive than appears externally. It is recognised clinically by the characteristic cauliflower growth at the orifice of the sinus, and by the offensive nature of the discharge. A similar epithelioma may arise in connection with a chronic ulcer of the leg. The cancer may infect the femoral lymph glands. The operative treatment is influenced by the extent of the disease in the soft parts overlying the bone, and consists in wide removal of the diseased tissues and resection of the bone, or in amputation.