Malignant Connective-tissue Tumours—Sarcoma
The term sarcoma is applied to any connective-tissue tumour which exhibits malignant characters. The essential structural feature is the predominance of the cellular elements over the intercellular substance or stroma, in which respect a sarcoma resembles the connective tissue of the embryo. The typical sarcoma consists chiefly of immature or embryonic connective tissue. It most frequently originates from fascia, intermuscular connective tissue, periosteum, bone-marrow, and skin, and forms a rounded or nodulated tumour which appears to be encapsulated, but the capsule merely consists of the condensed surrounding tissues, and usually contains sarcomatous elements. The consistence of the tumour depends on the nature and amount of the stroma, and on the presence of degenerative changes. The softer medullary forms are composed almost exclusively of cells; while the harder forms—such as the fibro-, chondro-, and osteo-sarcoma—are provided with an abundant stroma and are relatively poor in cells. Degenerative changes may produce areas of softening or liquefaction which result in the formation of cystic cavities in the interior of the tumour. The colour depends on the amount of blood in the tumour, and on the presence of the products of degeneration.
The blood vessels are usually represented by mere chinks or spaces between the cells. This peculiarity accounts for the facility with which hæmorrhage takes place into the substance of the tumour, the persistence of the bleeding when it is incised or ulcerates through the skin, and the readiness with which the sarcomatous cells are carried off and infect distant parts through the blood-stream. Sarcomas are devoid of lymphatics, and unless originating in lymphatic structures—for example, in the tonsil—they rarely infect the lymph glands. Minute portions of the tumour grow into the small veins, and, becoming detached, are transported by the blood-current to distant organs, where they are arrested in the capillaries and give rise to secondary growths. These are most frequently situated in the lungs, except when the primary growth lies within the territory of the portal circulation, in which case they occur in the liver. The secondary growths closely resemble the parent tumour. Sarcoma may invade an adjacent vein on such a scale that if the invading portion becomes detached it may constitute a dangerous embolus. This may be observed in sarcoma of the kidney, the growth taking place along the renal vein until it projects into the vena cava.
Fig. 55.—Recurrent Sarcoma of Sciatic Nerve in a woman æt. 27. Recurrence twenty months after removal of primary growth.
In its growth, a sarcoma compresses and destroys neighbouring parts, surrounds vessels and nerves, and may lead to destruction of the skin, either by invading it, or more commonly by causing sloughing from pressure. Inflammatory and suppurative changes may take place as a result of pyogenic infection following upon sloughing of the overlying skin or upon an exploratory incision. Once the skin is broken the tumour fungates through the opening. Sarcomas vary in malignancy, especially as regards rapidity of growth and capacity for dissemination. Certain of them, such as the so-called “recurrent fibroid of Paget,” grow comparatively slowly, and are only malignant in the sense that they tend to recur locally after removal; others—especially the more cellular ones—grow with extreme rapidity, and are early disseminated throughout the body, resembling in these respects the most malignant forms of cancer. They are usually solitary in the first instance, although primary multiple growths are occasionally met with in the skin and in the bones.
Many varieties of sarcoma are recognised, according to its structural peculiarities. Thus, in virtue of the size and character of the cells, we have the small round-celled and the large round-celled sarcoma, the small and the large spindle-celled, the giant-celled and the mixed-celled sarcoma. The lympho-sarcoma presents a structure similar to that of lymph-follicular tissue, and the alveolar sarcoma an arrangement of cells in alveoli resembling that seen in cancers. When there is a considerable amount of intercellular fibrous tissue, the tumour is called a fibro-sarcoma.
