Cancer, derived from the Latin word cancer, a crab, is the name applied to a particular kind of tumour or "new growth" affecting man and some of the lower animals. Tumours may be divided into two groups, innocent or benign, and malignant tumours; the latter being characterised by their rapid growth, infiltration of surrounding parts, and tendency, in some cases, to produce secondary or metastatic growths in distant organs. The term cancer was at one time generally applied to the whole malignant group of tumours; but the study of microscopical appearances has led to their division into two great classes: - Sarcomata, or tumours of connective-tissue origin, and Carcinomata, or true cancers, which are derived from epithelium. In the language of embryology sarcomata take origin from the mesoblast, carcinomata from the epiblast or hypoblast. A carcinoma, or true cancer, then, is a growth caused by epithelial multiplication, and possessing the power of growing indefinitely and of infiltrating surrounding tissues.
The annual death-rate from "cancer" is .5 per 1,000 living in England and Wales, the total death-rate from all causes amounting to about 20 per 1,000. So that about one death in every forty is due to cancer. Much attention has been directed of late years to the increase in the death-rate from cancer. Thus, for the years 1861-65 the rate was .37; this had increased to .45 for the years 1871-75, and had undergone further augmentation to .54 for the years 1881-85. This increase is, at all events to some extent, an apparent, and not a real, increase, and due to the fact that the progress of knowledge has led to better diagnosis, and to the recording of deaths as due to cancer which would in former times have been attributed, from ignorance of their real nature, to other causes.
Cancer is a much more fatal disease in females than in males (in the proportion of about 2 to 1). This is in accordance with the fact that the two most common situations of malignant growth are the female breast and the womb. It is a disease of late life, being very uncommon before thirty-five years of age. Most of the deaths recorded as due to cancer in young people, in the registrar-general's returns, are cases of sarcoma and not of true cancer.
Carcinoma is divided into four varieties known as scirrhus, colloid, encephaloid, and epithelial cancer, or epithelioma; to which is sometimes added adenoid, or glandular cancer, this last-named variety being, however, sometimes considered as a sub-variety of epithelioma, and known as cylindrical epithelioma.
Scirrhus, or hard cancer, is most commonly met with in the female breast and affecting the pyloric end of the stomach or other parts of the alimentary canal. In scirrhus of the breast a hard nodule forms and often gives rise to shooting pains; it gradually increases in size, the skin becomes adherent over it, and retraction of the nipple occurs-: before long the axillary glands become affected.
Microscopic examination of such a tumour shows it to be composed of a fibrous stroma infiltrated with epithelial cells. These cells occur in groups, enclosed in the bundles of fibrous tissue, forming alveoli. The epithelial growth, at first luxuriant, soon ceases at the centre of the tumour, and the fibrous tissue undergoes contraction; the cell infiltration continues to extend, however, externally, so that while the tumour increases in size at its periphery the inner portions become dense and indurated, resembling the tissue of a cicatrix or scar. The early diagnosis and removal of such a tumour is not infrequently followed by complete recovery; if, however, the growth has been present for some time, and particularly if the glands of the armpit have become involved, an operation is too apt to be followed by "recurrence." Encephaloid cancer differs from scirrhus in its more rapid growth, associated with which is a softer consistence and a deficiency of stroma, and consequent absence of the cicatricial contraction which is so marked a feature in the slow-growing scirrhus. The name encephaloid is derived from the soft brain-like appearance which this form of cancer presents. Encephaloid is rare, save when it occurs in internal organs (e.g. the liver) as a "secondary" growth.
Colloid cancer is really a variety of one of the already mentioned forms, in which a gelatinous or colloid degeneration has occurred.
Epithelioma, involves the surface of the skin or of a mucous membrane, and particularly affects the junction between mucous and cutaneous surfaces. Again, places where complex changes occur in the process of development are apt to be involved, and hence it has been supposed by Cohnheim that the new growth is connected with the existence of embryonic rudiments, the growth of which is arrested for a time but subsequently springs into activity. Again, epithelioma is peculiarly associated with chronic irritation or injury. The epithelial cells are of the flattened, scale-like type, they extend downwards from the surface into the connective tissue beneath, and on microscopic examination characteristic globular aggregations of cells, like the coats of an onion, known as "cell nests," are often seen.
An epithelioma usually first appears as a small ulcer with irregular surface and indurated borders. The ulcer increases rapidly in size, the discharge from it being very offensive. The lower lip, tongue, cervix uteri, and oesophagus are common situations to be affected by the disease.
The cause of cancer is involved in obscurity. It often presents itself in patients who give a "family history" of the disease; its geographical distribution throughout England and Wales is peculiar; the association of malignant new growth with chronic irritation must be something more than a mere coincidence. The age distribution has already been alluded to, and Cohnheim's view has been mentioned.
Modern investigation is being mainly conducted with a view to demonstrating the parasitic nature of the disease. Attempts have been made of late years to connect cancer with a low form of animal life allied to the Coccidium oviforme, a parasite commonly found in the liver of the rabbit (in the encysted form known as Psorospermiae). There is some reason for entertaining the hope that the time is not far distant when more may be known with respect to the causation of cancer, and if the essential nature of the disease be discovered much light may be thrown on means of preventing and possibly of curing it. At present the only method of dealing with the disease (beyond mere palliative measures) is by surgical operation. This to be effectual must be resorted to early. If the morbid process has been allowed to spread at all widely, and particularly if the neighbouring lymphatic glands have become involved, it is but too likely that the disease cannot be completely removed, and that it will recur after operation. Hence the paramount importance of early diagnosis.
Many forms of disease simulate cancer, and if the medical man is called in, it will in many cases be his pleasant duty to allay the apprehensions of his patient, but on no account should anyone who has the merest suspicion of cancer omit to at once obtain skilled advice.
Cancer curers have imposed upon the credulous from time immemorial, and secret remedies still fascinate those who despise or are ignorant of scientific inquiries and methods. Some of them may work but little direct harm; yet, by reason of the caustic properties they possess, if applied to a benign form of tumour they will gradually and painfully eat it away, and so obviate the much more satisfactory and much less painful use of the knife; others are actively injurious, all are alike productive of mischief if they delay for a time the obtaining of competent professional advice, in a disease the early recognition and proper treatment of which is of such vital importance to the patient.