4. Spontaneous Tumours, or Tumour; Proper (synonyms: Neoplasm, New Growth).-~The following definition of a spontaneous tumour suggested by Ziegler is perhaps the most satisfactory: "A neoplasm or tumour is a new formation of tissue, which is atypical in structure, serves no useful purpose to the whole economy, and the growth of which has no typical termination. " in this definition the words “ new formation of tissue” exclude the cystic swellings; the attribute “ atypical in structure " excludes hypertrophies; and the final clause “ the growth of which has no typical termination" excludes all swellings of an inflammatory nature which progress, however slowly, towards either suppuration or resolution and recovery.
These tumours arise by the exaggerated and abnormal proliferation of a single cell, or a group of cells. They increase in size solely by the multiplication of their own cells, and the only contribution which the surrounding tissues make to the progress is the formation of a “ stroma, " or supporting framework of fibrous tissue; and even that is wanting in many cases. lnasmuchas the newly-formed cells of the tumour take on the likeness of the parent from which they are sprung, it follows that the minute structure of such a tumour, whatever its situation, will be a more or less exact copy of that of the tissue whence it ori inated. A tumour growing from the skin will therefore imitate tire cell-structure of the normal skin; the resemblance of a breast tumour to the healthy breast is often so close as to make it a hard task to distinguish the one from the other; whilst the similarity of bony and cartilaginous tumours to true bone and cartilage is evident to all. r-This
imitation of the parent type by the spontaneous tumours is one of their most remarkable characteristics, and provides a reliable criterion by which they may be separated from the inflammatory new growths, which are all built u on the same general plan. Consequently it is almost always possible to determine the origin of a tumour from an examination of its histological appearances; and conversely we know that an epithelial tumour will never spring from a connective tissue nor a connective tissue tumour from an epithelium.
Another outstanding feature of the neoplastic tumours is that they lead an entirely independent existence subject to none of the restraints to which the normal cell must needs submit. These normal cells are, indeed, possessed of certain limited powers of multiplication, by which they are enabled to replace the slight loss of tissue which the wear and tear of life perpetually entails; or, again, the can on occasion make good a greater loss of substance, as in the liiealing of an ulcer, or the regeneration of a skin wound. But these powers are confined within certain well-marked bounds, which may not be transgressed. Contrast with this the tumour cell, emancipated from all control and owning to no restraint. It is true that the simple tumours often remain stationary after attaining a certain size, but the general tendency of ali tumours is towards persistent and unlimited growth, and the cancer cell continues its career unchecked by everything save death.
The spontaneous tumours are seen in every tissue and organ of the body, though in some they are relatively infrequent. Nor are they confined to man, for they have been found throughout the vertebrate kingdom. It is often stated that a higher state of civilization has inflicted on European races a greater susceptibility to tumour formation. As to this, reliable evidence is hard to obtain, but such a statement would seem to be only partially true, and the apparent immunity of certain native races is to some extent due to lack of sufficient observations.
It is usual to separate these tumours into two groups: the Nonmalignant, Innocent or Benign, and the Malignant or Cancerous. Of these two groups the latter are the more familiar and have attracted much more attention and study than the former, on account of the danger to life which they involve, but in point of numbers they are greatly outweighed by the first group. Two or more nonmalignant tumours, of the same or different varieties, are often found in the same individual; but with the cancers this is a rare occurrence, and such growths are usually single. The non-malignant tumours are usually rounded in shape. In size they vary enormously; a fibroid tumour may be as small as a pea; a fatty tumour may weigh forty pounds. Often they cease growing after attaining a certain size, but there are very many exceptions to this, and it is seldom possible to predict the subsequent course of one of these growths. They possess, however, four constant characteristics by which they may be distinguished from the malignant variety.
I. A non-malignant tumour, whatever its size, remains localized to the part from which it originates. It is not an “ infiltrating ” growth, that is to say it does not eat its way into the surrounding tissues, but rather pushes them aside, and so may be called “ expansive. " Moreover, it is separated from them by a thin but usually well-marked layer of fibrous tissue known as the “ capsule " of the tumour, which seems to be formed as the result of a slight inflammation that the presence of the tumour always causes among the healthy tissues surrounding it, and may be regarded as a protest on their part against the invasion of the tumour. 2. Non-malignant tumours are not of themselves dangerous to life. They may, however, cause a great deal of pain and even death, when situated in some sensitive or delicate organ.~ For instance, a small tumour may cause intense pain by pressing on 1 nerve, or dropsical swelling of a limb by obstructing a vein, or death from suffocation by blocking the larynx. Nevertheless it remains true that any evil effects are due not to the nature of the tumour, but to its situation, whereas a cancer causes death whatever its position.
3. These tumours never reproducethernselves in distant pa-rts of the body. More than one may be present in the same individual, but each arises independently, and the widespread dissemination so typical of a cancerous growth is never seen.
4. An innocent growth never recurs after operation. The boundaries of the growth are so well defined that complete removal is usually easy, and the operation is a simple and satisfactory proceeding.-Malignant
Tumours, or Cancers.-There are two varieties of malignant tumour: the Sareomata, arising from the' connective tissues; the Carcinomata, arising from epithelial tissues. » It is customary to describe them both as cancers. The main features of these tumours are as follows:-
I. The Injiltrating Nature of a Malignant Tumour.—A cancer follows a course very different from that of an innocent tumour. Its growth has no appointed termination, but continues-with unabated vigour until death;. moreover, it is more rapid than that of the innocent tumours, and so does not permit of the formation of a capsule by the neighbouring tissues. In consequence such-»a tumour shows no well-defined boundary, but from its margin fine tendrils of cancer cells make their way in all directions into the surrounding parts, which gradually become more and more involved in 'the process. Thus a cancer of the breast will attack both the skin covering it and the underlying muscle and bone; a cancer of the intestine will eat its way into the liver, spleen and kidney, until these organs becomeito a great extent replaced by cancer cells, and can no longer perform their proper functions. .
2. Formation of Secondary Growths, or Metastases.—In addition to this spread of growth by direct extension, another characteristic of malignant tumours is a tendency to dissemination, that is, to reproduce themselves in various parts of the body far removed from the original site; so that it is not unusual to find after death that a cancer of the breast has?given rise to secondary, or metastatic, deposits in the lymphatic glands, the lungs, the ribs and other bones, the brain and the abdominal organs. These secondary deposits are due to the tumour cells making their way through the walls of the small lymph and blood vessels and becoming detached by the force of the circulation, by which they are carried to some distant part of the body, there to continue their career of uncontrolled growtlh ' r
The sarcoma ta and carcinoma ta differ somewhat as regards the path of dissemination. The former are vascular tumours, well supplied with blood-vessels; consequently dissemination usually occurs by way of the blood-stream rather than by the lymphatic circulation, and the commonest site for the secondary deposits of sarcoma is the lung. The carcinoma ta are less vascular, and the tendency of the growth is to invade the small lymph channels, so that the first signs of metastases are to be looked for in the lymphatic glands; at a later date these deposits may be spread throughout the body, particularly in the liver and other abdominal organs, the lungs and the bones.
The formation of metastases is of the utmost importance from a clinical point of view, as the suceessof an operation depends on the removal of all the secondary deposits as well as of the original growth. For instance, a few months after the first appearance of a cancer of the breast the axillary lymph glands will be found to be hard and enlarged. This means that some of the cells of the primary growth have been carried in the lymph stream to these glands, and have begun to grow there; consequently any operation for the removal of the cancer of the breast must include the removal of these glands. If the breast tumour only be taken away the rowth will continue unchecked in the glands. It is a matter of great difficulty to determine by the naked eye or the touch whether a gland is infected or not. In man cases where there is no evident enlargement the microscope will show the presence of cancer cel1s; and a certain opinion can only be given after a microscopical eX3.l'1'11l'latlOX'l. Y
In operations for cancer of the breast or tongue the modern practice is to regard the lymphatic glands of the axilla or neck respectively as infected in every case, however early it be, and to remove them accordingly. In other parts of the body where the glands are inaccessible, the only solution of the difficulty is to urge the removal of the tumour at the earliest possible moment, before lymphatic infection has had time to occur.
The frequency and rapidity of metastasis- formation varies greatly. As a general rule cancer of the breast is more liable than other forms of growth to be followed by widespread secondary deposits. On the other hand, in cases of cancer of the skin secondary infection is usually confined to the neighbouring lymphatic glands, and seldom occurs in any of the internal organs. 3. Termination of Malignant T umours.-In one or two well authenticated cases a malignant tumour has disappeared of its
