The carcinomata spring from the epithelial type of tissue while the sarcomata emanate from the connective tissue type.
Origin. Tumors originate from many causes. Some are congenital and others grow in later life from an inherited tendency.
Any continued irritation which acts mechanically or chemically so as to maintain a constant, though slight, degree of undue vascularity of a part, such as the hot, rough stem of a clay pipe or a jagged tooth, favors the development of a malignant growth. Certain benign growths, such as warts or moles, are especially prone to malignant change. Age and sex also predispose to tumor formation.
Thus carcinoma is a rarity under thirty years of age; the mammary gland of the female is more liable to carcinoma than the male; while on the other hand the esophagus, lip and tongue of the male are more liable to attack.
The possibility of certain malignant growths being of germ origin is thought to be evident (though not yet proven) from many facts. The fact that where there are malignant growths present, lymphatic glands, quite distant from the original growth, become secondarily infected, through the lymphatic vessels, seems to carry out this view.
Particles of a carcinoma (metastasis) floating in the blood stream, finding lodgment elsewhere also establish new growths (metastatic).
Tumors are named according to the tissues from which they arise, thus:
Connective Tissue Tumors
Fibrous tissue——Fibroma
Fatty tissue——Lipoma