CANCER. Nature of Cancer.— A tumor is a growth of abnormal size and situation, com posed of cells of the body. Some tumors are not dangerous to life, because they do not in crease after they attain a certain size; others, and these are cancers, have no limit to their growth, and destroy life by extending into healthy tissue or by interfering with digestion or some other important vital function. While a cancer is a particular sort of tumor, there are also many varieties of cancer; and these vari eties are classified according to the tissue from which the growth originates. If the cancer be gin in the skin or epidermis, it is called an epithe lioma; if it begin in a gland, it is called a carcinoma; if it begin in muscle, fibrous tissue, tendon or bone, it is called a sarcoma. These kinds of cancer grow progressively and are fatal if not promptly removed.
In the beginning a cancer is composed of a few microscopic cells, much smaller than the point of a pin. Depending upon the type, it may grow in a months to the size of a grape fruit, or may require years to reach the size of a pea. When it first begins to grow there are no symptoms— no pain and no bleeding; but later, when the cancer presses on the nerves, pain results. Bleeding begins only when the cancer ulcerates. Any other symptoms to which a cancer may give rise are due solely to its interference with some normal function of the body. A cancer looks like a lump of tissue. It has no roots, as is popularly believed, but it may grow out through the vessels of the body to distant parts.
Cancer is not a new disease but one which has been recognized since earliest times. It is mentioned by the Egyptians in the Papyrus Ebers, and by the Hindus in their medical writ ings, both of which probably date back to about 2000 Occurrence of Cancer.— While cancer oc curs not only in man hut in all warm-blooded animals, it is not equally frequent at all ages.
Certain types of cancer may be found in a new born infant, in other words, are congenital; but these are very rare. The usual rule is that cancer begins to appear at the age of 35, and increases rapidly in frequency until the age of 65— a little earlier in women, a little later. in
men. After 75, the rate of occurrence of cancer decreases very rapidly, until it practically dis appears at 90. The same frequency distribution according to age is seen also in mice, rats, dogs, cats, etc.; that is, the disease appears only in older animals, but is less often seen in the very old.
Sex Variations.— Sex has some influence on the rate of occurrence of cancer; for ex ample, between the ages of 35 and 45, men show the disease less often, practically only one-third as often as women; between the ages of 55 and 65 the frequency in men is about 65 per cent of that in women of corresponding age; while in old age, men have more cancer than women. This is due to the fact that in women a great many cancers occur in the breast and in the womb at about the beginning of the change of life, that is, from 45 to 50 years of age. On the other hand, cancers of the lip and tongue attack men only, practically; and these, with cancer of the skin, appear late in life. Similar variations in the occurrence of cancer are noted also in the different organs of the body; for example, the more frequent site for cancer is either the stomach or the liver. Thus, while in 1913, in the United States, 30,205 people died of cancer of the stomach or of the liver, only 2,633 died of cancer of the skin, and 3,007 of cancer of the tongue and mouth.
Race Variations.— The differences noted in the occurrence of cancer in organs are also noted in the occurrence of cancer in different races; for example, the negro race is attacked by cancer much less frequently than the white race, and cancer seems to be more frequent in people of the northern European states than it does in those living in the tropics or in South America, although the population of South America is much the same as that of Spain. There is, also, a difference in the organ dis tribution in different countries. In England and Wales, out of 100,000 women, 18.6 indi viduals will have cancer of the breast, while in Japan, only 1.8 women out of 100,000 will suffer from the disease. The occurrence of cancer of the skin in the negro race in the State of Mary land is only half that in the white population.