IN its literal meaning this term simply indicates a fleshy tumour, and it was formerly applied in a very indefinite way. Under the influence of Virchow, however, it has come to include a group of tumours, which, though in certain respects differing in structure, yet present such features in common that .they form a consistent class of themselves.
The sarcomas may be defined as tumours which originate in one or other of the forms of connective tissue, but differ in structure from their mother-tissue chiefly in respect that the cells greatly preponderate over the intercellular substance, and also that they frequently differ greatly in size and shape. This definition includes the origin of the tumour, and refers also to the atypical character of the structure. It may be added that in its mode of growth the sarcoma is also atypical, having the characters of malignancy already referred to.
Sarcomas have been somewhat aptly compared in structure to inflammatory new.formations. We have already seen that the tendency of these, as exemplified in the granulating wound, is to develop into connective tissue. The round cells pass into spindle cells, and then the connective tissue develops out of the latter. The round and spindle cells may thus be regarded as the preparatory, or in a certain sense embryonic stage of connective tissue. In sarcomas we have tumours composed of round cells, and tumours composed of spindle cells, with little or no tendency to further development, as if the embryonic form had been stereotyped for the whole life of the tumour. Besides these forms sarcomas sometimes contain giant-cells (myeloplaques). We know that cells of this nature occur normally in growing bones where, as Wegener and Kolliker have shown, they exercise an important function (osteoclasts), and they are not unknown in granulation-tissue, even apart from bone. They also are to be regarded as connective tissue structures, and as belonging to a developmental stage of connective tissue.
From the definition given above of sarcoma it will be apparent that the tumours included in this class will vary very greatly in structure and other characters. They will vary in the first place according to their tissue of origin, because, although in general following the type of granulation-tissue, yet they usually carry with them, especially in the characters of the intercellular substance, some indications of the mother-tissue, so that it might be possible to distinguish as many forms of sarcoma as there are typical tumours of the connective tissue series. But even when derived from the same tissue the tumours may vary according to shape, size, and abundance of cells, so that still greater complexity is thus introduced.
In the diagnosis of actual cases reference should be made to origin as well as to structure and mode of growth.
Sarcomas differ according to the form of cells and character of intercellular substance. So far as the Cells are concerned the chief forms are those already mentioned, namely, round, spindle-shaped, and giant-cells. The tumour is usually homogeneous in its structure, at least in its recent parts where not altered by degenerations or further developments, and so it is generally possible to distinguish sarcomas according as they are round-celled, spindle-celled, or giant-celled. There are, however, cases in which the cells are variously shaped, partly round and partly spindle-shaped. •
As the characters of the individual forms of connective tissue are determined by their Intercellular substance, so in sarcomas the shape of the cell does not bear a constant relation to the character of the intercellular substance. Sarcomas are sometimes named according to their relations to the various connective tissues, thus Fibrosarcomas, Myxosarcomas, Chondrosarcomas, and so on. We even have tumours of striated or smooth muscle which take on the sarcomatous mode of growth, and are hence called Myosarcomas.
The Blood-vessels of sarcomas are generally rather thin-walled, and they run usually in immediate contact with the tumour tissue. In some cases they are supported by complete or rudimentary connective tissue, which may divide the tissue into alveoli, and so give rise to an appearance resembling that of cancer (alveolar sarcoma). Sometimes the sheath of the vessels undergoes a peculiar transformation into a hyaline substance, which forms a mantle round the vessels, and gives a plexiform character to the tissue (plexiform sarcoma, cylindroma).
Pigmentation is not infrequent in sarcomas, especially in those arising in pigmented situations such as the skin and eyeball. The pigment is usually in the cells, but may be in the intercellular substance.
As connective tissue is of nearly universal occurrence, sarcomas may arise in almost any situation. They originate, however, for the most part where connective tissue in some form is abundant. Thus the bones, the skin, the mammae, and the lymphatic glands are frequent seats of origin. They are also common in the testicles and the brain, but. are rare as primary tumours in other glands, in the muscles and in the lungs.
The place of origin has an important iufluence on the structure of the tumour and on the transformations and degenerations to which it is liable.
The sarcoma grows by multiplication of its own elements, and it is often surrounded by a capsule so as to be apparently self-contained. Even when so delimited, however, it generally presents the characters of local malignancy. The tumour grows along the existing connective tissue of the part, and outside the apparent boundaries, even outside the capsule there are already the multipljnng cells of the tumour.
This was very characteristically observed by the author in a case of pigmented sarcoma, where the pigmented cells were plainly visible in the connective tissue outside the mass of the tumour.
Besides this local malignancy, sarcomas frequently give rise to Secondary tumours at a distance. As a general rule the lymphatic glands are not secondarily affected, but in sarcomas of the foot, the tonsil, the testicle, and probably the kidney, they are liable to be involved (Butlin). This fact implies that either in their origin or in process of growth the sarcomas of these localities come into relation with the lymphatic vessels. Either with or without an intermediate affection of the glands extension is liable to occur by the blood so aa to reach the lungs, which are the most frequent seats of such metastatic growths. It may pass on by the systemic circulation to a large number of different situations. The secondary tumours repeat exactly in structure and mode of growth the primary one, so that we may have, in the lungs or elsewhere, typical spindle-celled tumours, or even cartilaginous or ossifying sarcomas.
The sarcomas are somewhat liable to metamorphoses and transformations. The soft and quickly growing ones are specially prone to fatty degeneration and softening, so that cysts may form in this way. Then the tissue may show a tendency to develop into the mature tissue of its kind. Thus a fibrous development may occur in the sarcomas of membranes, or a partial formation of cartilage or bone may take place, and this tendency may be so marked as to give a distinctive character to the tumour, so that we may speak of an Ossifying, Indurating, or Calcifying sarcoma. This peculiarity may give rise to mistakes in diagnosis if a part of the tumour which has undergone transformation be examined, hence it is always proper to seek for the growing margin of the tumour for examination.
Besides this the sarcomatous tissue may be mixed with other tissues. Gland-tissue is most frequently thus associated, especially in the mamma and testicle. It is sometimes difficult to determine whether the gland-tissue found in mammary tumours is simply the remains of the gland or new-formed. The presence of gland-tissue is important as the latter frequently, by dilatation, gives rise to Cysts. These cysts frequently give a special character to the sarcomas, especially in the mamma and testicle, the association being indicated by the term Cystic sarcoma. The tumour tissue often grows into the cysts,, forming the so-called Intracystic growth, and often giving a peculiar character to the tumour when divided by the knife.
Sarcomas coming to the surface usually incorporate the skin, converting it into their own tissue, and then Ulcerate. The ulcer is thus formed of the tumour tissue, which may be excavated by softening, or may pout outwards into a fungating mass, liable to bleed (Fungus hamatodes).
The most convenient division of sarcomas is according to the form and other characters of their cells. While such a division is adopted, however, it must be remembered that tumours occur in which various forms of cells are present.