n. [capitalized] [NL.] In zoology, the typical genus of brachyurous decapodous crustaceans of the family Cancridæ: formerly more than conterminous with the order Decapoda, now restricted to the common edible crab of Europe, C. pagurus, and its immediate congeners. See crab.n. [capitalized] In astronomy, a constellation and also a sign of the zodiac, represented by the form of a crab, and showing the limits of the sun's course northward in summer; hence, the sign of the summer solstice (marked ♋).n. In pathology, a malignant tumor technically named carcinoma (which see); also, by extension, any malignant tumor, as one of certain adenomata and sarcomata.n. A plant, possibly cancerwort.n. The term cancer, as commonly employed, includes those new growths which possess certain attributes that render them especially dangerous to life, and which are therefore called malignant. Malignant tumors growby infiltration and destruction of the surrounding tissues, and are characterized by a tendency to recur after removal, by the property of spreading to other parts of the body by a process of dissemination known as metastasis, and by producing a general disturbance of health termed cachexia. From the standpoint, of the pathologist two chief groups of cancerous tumors are recognized: the carcinomata, or true cancers, and the sarcomata. The fundamental difference between these two is the fact that carcinoma originates in the epithelial tissues of the body, whereas sarcoma develops from the connective tissues. This difference in origin gives rise to certain structural characteristics which enable the microscopist readily to distinguish one type from the other. Carcinoma is rare before the age of thirty; it is somewhat commoner in women than in men; and it is most often seen in the uterus, skin, breast, and stomach. Sarcoma is a disease of early adult life, is more prone to attack men than women, and is commonly found in the subcutaneous tissue, bony structures, and lymph-nodes. Carcinoma is conveyed from one part of the body to another through the lymphatic vessels, sarcoma by way of the blood-stream. In spite of an enormous amount of research devoted to this subject, the exciting cause of cancer is still unknown. The influences of heredity, climate, food, race, social condition, and local injury have all been invoked as factors concerned, but without arriving at any degree of certainty. The theory referring the developmentof malignant tumors to the presence of minute animal or vegetable organisms has numerous adherents, but it has not been definitely established, and many prominent authorities consider that the explanation is to be sought for in a disturbance of some still undiscovered fundamental law governing the growth of cells. Although it appears that cancer is increasing somewhat in frequency, the percentage of cures is increasing much more rapidly, owing to the earlier diagnoses and more thorough operations which are now possible. Extirpation by the knife as promptly and as completely as possible, when the growth is accessible, is regarded as the method of treatment that offers the greatest hope of a cure; but the employment of the X-rays or other form of radioactivity has in a number of instances given excellent results.n. Figuratively, a moral or social evil likened to a cancer in its malignant character and corroding tendency: as, “sloth is a cancer,”To corrode or eat into, in the manner and with the steadily destructive persistency of a cancer.
