Cancer (Lat., 'a crab'), or CARCINOMA (Gr.), is the medical name for an important group of malignant tumours (see TUMOUR). The term cancer used to be applied to malignant tumours generally, but recent research, with the aid of the microscope, into their structure has led to their division into two groups—Carcinomata and Sarcomata (q.v.); and cancer is now used only of the first. To prevent confusion, carcinoma is generally used in preference to cancer in scientific works, but the more familiar name will be retained here.
Cancer may be defined as a tumour consisting of masses of cells of an epithelial type, grouped together irregularly within the spaces of a framework of fibrous tissue. The form of the cells, as seen under the microscope, usually corresponds in some degree to that of the normal epithelium of the part in connection with which the primary tumour has developed, and on this the classification of the different forms of cancer is partly based. Flat-celled cancer or epithelioma occurs most commonly as a primary tumour on the lips, tongue, penis, and near the anus; Columnar-celled or adenoid (gland-like) cancer, in the stomach and intestines. Scirrhous or hard, and encephaloid or soft cancer, have cells of less characteristic form, but usually more or less rounded, and differ from each other structurally only in the greater or less abundance of the fibrous framework. They are most common as primary tumours in the female breast, the womb, and certain parts of the alimentary canal. Colloid cancer is a hard or soft cancer in which the cells undergo rapid and extensive degeneration into a gelatinous mass.
These different forms of cancer differ widely in their rate of growth and degree of malignancy. Epithelioma is the slowest in its progress, and comparatively rarely gives rise to growths in internal organs. Soft cancer usually grows with great rapidity, and secondary tumours in internal organs are apt to appear early.
The general structure of the secondary tumours usually corresponds to that of the primary; but they are often softer and show greater activity of growth, so that when they appear the progress of the disease is accelerated. These secondary tumours are believed usually to result from a transference of infective elements from the primary growth, either in the lymph or the blood, to some resting-place where they determine the growth of a new tumour. The lymphatic glands in the neighbourhood of the primary growth are usually first affected, and are by far the most constant site of secondary growths. But any portion of the body, even the most distant, may suffer; most commonly the liver or the lungs.
The symptoms attending the early development of cancer, even cancer affecting the same part of the body, are very variable. If the disease affect an external organ or tissue, the tumour is generally noticed at an early stage; if an internal organ, on the other hand, some disturbance of its functions, or pain, or general deterioration of the health often appears before the presence of a growth is suspected. But wherever or however it begins, a cancerous tumour always tends to increase, with breaking down of the older portions, ulceration, and fetid discharge, to encroach upon neighbouring tissues, to set up secondary growths, and ultimately to cause the death of the patient. The cases where an undoubtedly cancerous tumour has spontaneously disappeared are so very rare, that the above statement, for practical purposes, hardly needs qualification. The duration of the case may be a few months or many years, according to the part affected and the malignancy of the tumour. The symptoms produced, and the mode in which the disease causes death, are almost as various as the organs affected. But in the later stages there is nearly always loss of appetite, flesh, and strength, and a peculiarly unhealthy, sallow appearance. Cancer is popularly believed to be an intensely painful disease, and in many cases really is so; but it is most important that it should be known that it may, and often does, run its whole course to the fatal issue without any pain whatever.
The causation of cancer is a most complex and obscure problem. It is rare before middle life, and after that period becomes increasingly frequent as age advances. The tendency to its development is frequently hereditary. It is more common in the female sex, because the womb and female breast are its most common situations; excluding these organs, it is probably more common in the male than the female. It sometimes occurs in situations where an injury has been sustained, and more frequently where there has been long-continued irritation. But here our certain knowledge with regard to it ends. It has been maintained by some that cancer is always from the first a constitutional disease; that the local tumour is merely an expression of a vitiated state of the constitution, or cachexia, and therefore that its removal is useless. But it is undoubted that in the vast majority of cases the patient's health is otherwise good when the growth begins, and that it remains for a time limited to its original seat; moreover, cases are not uncommon where early removal of the primary tumour has been followed by no return of the disease. It seems reasonable therefore to conclude that cancer is at first a merely local process, at least in many cases, and only secondarily becomes a constitutional disease.
The analogy between the behaviour of cancer and that of certain diseases known to be produced by microscopic parasites (e.g. leprosy, tuberculosis) has led to a suspicion that some such agent may be present in cancer too; but no positive evidence has yet been found in support of this view.
The leading character of cancer being a tumour or morbid growth in a part, it is important to observe that not all, nor even the majority, of morbid growths are cancerous. A very large proportion of growths, involving swelling or change of structure in a part, are either determined by a previous process of inflammation—leading to chronic abscess and induration—or belong to the simple or non-malignant order of tumours.
Now, the practical distinction, or diagnosis, to use the technical phrase, of these different tumours is founded upon a very careful and delicate appreciation of the characters of the malignant and non-malignant tumours, considered as morbid products, and also upon a thorough knowledge of the anatomy and relations of the textures in which they arise. The attempt, therefore, to determine the character of a particular growth must always call for the highest qualities of the surgeon—large experience, minute and thorough knowledge of natural and morbid structure and function, and a full and judicial consideration of all the various facts of the case. Indeed the difficulties of the inquiry are such that even in the dead body, or in a tumour excised from the living body, all the resources of the anatomist, aided by the microscope, will occasionally fail in distinctly and surely discovering the true character of the morbid structure.
Generally speaking, a tumour may be said to fall under the suspicion of being cancer when it more or less completely infiltrates the texture in which it arises, and passes from it into the surrounding textures; when it invades the lymphatic glands adjoining the part first affected; when it is attended by stinging or darting pains, or by obstinate and slowly extending ulceration, not due to pressure; when it occurs in a person having impaired health, or past the middle period of life, and is not traceable to any known cause of inflammatory disease or local irritation, nor to any other known constitutional disease, such as syphilis or scrofula. The probabilities are of course increased if the tumour be in one of the habitual seats of cancer, or if it be attended by evidence of disease in some internal organ known to be frequently thus affected. But it is hardly necessary to point out that the very complex elements of diagnosis here referred to ought to be always submitted to the scrutiny and judgment of a well-educated medical adviser, whose skill and personal character place him above suspicion, before the disease has assumed such a form as to be beyond the reach of remedial procedure. The patient who broods in secret over a suspicion of cancer, or who declines to apply for advice from a fear of encountering the truth, is in all probability only cherishing the seeds of future suffering; while if, as often happens, the suspicion is unfounded, a few minutes' careful examination would suffice to remove a source of misery which otherwise would poison the mind for years.
These remarks apply still more emphatically to the misguided persons who trust to the non-professional cancer-curer, or to the quasi-professional specialist. The charlatan who pretends to hold in his hands a secret remedy for this most terrible disease, will invariably be found to pronounce almost every tumour cancer, and every cancer curable. By this indiscriminating procedure, and by the fallacious promise of a cure without an operation, many persons who have never been affected with cancer at all, have been persuaded to submit to the slow torture of successive cauterisations by powerful caustics, at the expense of needless mutilation and no small risk to life. In other cases, truly cancerous tumours have been removed slowly and imperfectly, at the cost of frightful and protracted sufferings, only to return at the end of a few weeks; and Sir Spencer Wells has shown that in some notorious instances persons were reported as cured when they had actually died of the disease at no long period after the supposed cure was stated to have taken place. (Cancer and Cancer-curers, 1860.)
The occasional spontaneous disappearance of cancerous tumours alluded to above warrants the hope that a means may some day be found of inducing by drugs or otherwise the occurrence of a curative process thus shown not to be beyond the possible. As yet, however, it is only a hope; for none of the many remedies that have been suggested has ever stood the test of experience. The only means of cure yet recognised is complete removal of the tumour by operation or by caustics. It is only in the earliest stage of the disease that there is any prospect of a successful result; and unfortunately the majority of patients present themselves to the surgeon when that stage has passed. Moreover, even in cases where the tumour has been early and freely removed, recurrence too often disappoints the hopes of the patient and the surgeon. But when the tumour is seen early, when there are no secondary growths, and when the patient's health is good, it is considered by the great majority of surgeons that he should be given the chance of cure which an operation affords.
In aged persons the question often resolves itself into a calculation of the chances of life, founded on a great number of conflicting data, and only to be solved by a careful attention to the state of the general health, as well as to the rate of progress of the local disease. Operations are now very rarely performed after the lymphatic glands are involved, or when there is evidence of a deteriorated constitution, or of internal disease; but sometimes great pain, or profuse and exhausting discharge from an external tumour, may justify its removal, as a palliative measure, even under these unfavourable circumstances. For the mode of removal of cancerous and other tumours, see TUMOURS; and see also the articles HEART, STOMACH, &c.
Among the lower animals this disease is more rare; nevertheless, cases are not unfrequent, presenting the same malignant characters as those observed in the human subject.