IV. PATHOLOGY OF TUMORS.

THE form of a tumor depends largely upon its location and on the structure of the tissues in its immediate neighborhood. A tumor developing from a surface and projecting beyond it, with a wide base, is said to be "sessile." If the tumor becomes more prominent and the base narrows, a pedicle forms, when it is called a "pedunculated" tumor. Such tumors attached to a mucous membrane are usually described under the term "polypus." If a tumor originates from a part surrounded by tissues offering the same degree of resistance, it usually assumes a globular or an oval shape. If it occupies a locality covered in by a broad resisting structure, it becomes flattened out, as is the case with intra-articular lipoma, called lipoma arborescens. Unequal resistance over the surface of the tumor moulds it in all imaginable shapes. The surface of the tumor may be smooth, lobulated, or nodular. Benign tumors are usually smooth; lipoma is often lobulated; sarcoma is either smooth or lobulated; carcinoma is nodular. The density of a tumor depends on its structure, the character of the tissues in its immediate vicinity, and the degenerative changes that have taken place. A tumor composed largely of parenchyma-cells is usually soft; tumors supplied with a well-developed stroma are hard; a tumor composed almost exclusively of blood-vessels (angioma) is greatly reduced in size under pressure; a tumor with liquid contents (cyst) ordinarily presents fluctuation; a solid but soft tumor (lipoma and sarcoma) is often mistaken for a cyst or an abscess, because on palpation a sense of fluctuation can be felt (pseudo-fluctuation). The color of tumor-tissue is greatly influenced by its vascularity, the character of the cells of which it is composed, and the extent and nature of the degenerative changes which have taken place. Most of the benign mesoblastic tumors present a whitish appearance. Sarcoma, as its name indicates, resembles on section flesh. The cut surface of a firm carcinoma is very similar in appearance and density to a raw turnip. Fatty degeneration of the contents of the alveoli imparts to the cut surface of the tumor a yellowish tinge. Hemorrhage into the substance of a tumor produces pigmentation of various degrees, from almost black to a yellow tinge. The black color of melano-sarcoma and melano-carcinoma is a distinguishing feature of these forms of malignant tumors.

Tumor-tissue, stroma and cells, is subject to the same pathological changes as the normal tissues of the body. Among the more important of these changes are the regressive metamorphoses of the cellular elements.

Fatty Degeneration.-Fatty degeneration of the parenchyma-cells of a tumor is one of the most frequent secondary pathological changes observed in tumors. The immediate cause of this form of degeneration is a defective blood-supply; hence it occurs most frequently in old benign tumors and in malignant tumors in which vascularization does not keep pace with the increase of tissue. It is a constant occurrence in slowly-growing carcinoma of the lip and the breast. In ulcerating surface epithelioma the fatty material can be squeezed out from the alveoli in yellowish-white masses resembling the contents of a small retentioncyst of the sebaceous glands. In glandular carcinoma the alveoli which have undergone this change present themselves on the cut surface as yellow areas of variable size, from which the same kind of material escapes under pressure. If this material is examined under the micro

scope, nothing but a granular detritus can be seen, with here and there a fat-crystal (Fig. 13) or a cholesterin-plate (Fig. 14). The fatty change commences as an infiltration of the cells, this infiltration finally resulting in the breaking up of the cells into granular matter. The distinction of cells by this or by any other form of regressive metamorphosis retards tumor-growth; but while the growth has become stationary at one place it continues in other places, so that a tumor is seldom entirely removed by degenerative changes. Degeneration commences either in the oldest part of the tumor or in parts of it which by accident have been deprived suddenly or gradually of an adequate blood-supply. It is upon this well-known and thoroughly established pathological fact that surgeons

have made an attempt to imitate and anticipate the natural for which tend to limit or to arrest tumor-growth by cutting off the blo supply from the part, as suggested by Wölfler in the treatment

FIG. 14.-Cholesterin-plates; X 250 (after Perls).

tumors of the thyroid gland, and by gynecologists in ligation uterine arteries in the treatment of non-malignant tumors of the u Mucoid Degeneration.-The transformation of active tumo into a harmless, innocent mucoid substance has been observed in t belonging to the connective-tissue type, fibrom chondroma, and also occasionally in adenoma. part of a tumor which undergoes this form of eration becomes cystic.

FIG. 15.-Colloid degeneration of the epithe

lial cells of a cancerous tumor of the mamma;

ilton).

Colloid Degeneration.-The exact chemical position of colloid material has not been deter Scherer regards it as an albuminous substa combination with a carbohydrate analogous to

X 400 (after D. J. Ham- and metalbumin. Colloid material is a jell structureless substance derived by a degen process from the parenchyma-cells or the stroma of a tumor. form of degeneration takes place in both benign and malignant t but is observed most frequently in tumors of the thyroid gland, ovary, and of the gastro-intestinal canal. If the parenchyn undergo this change, the colloid material appears in the prot of the cell at one or different points, and the process continue the cell-walls give way, when the colloid material is liberated (F

1. Corpora amylacea, cyst of choroid plexus; X 85 (laboratory of Rush Medical College, Chicago): a, connective tissue; b, b, corpora amylacea; c, longitudinal section of blood-vessel; d, transverse section of blood-vessel. 2. Malignant tumor of orbit: a, connective-tissue capsule; b, number of embryonic cells; c, hyaline substance; d, embryonic cells in capsule.