XX. CHONDROM A.

CHONDROMA is a tumor which, according to its structure, is a close imitation of hyaline, reticulated, or fibrous cartilage. It occurs in parts of the body in which cartilage exists in the fetus, as in the epiphyseal extremities of the long bones, or it springs from an island of displaced cartilage-cells, as in the connective tissue, the parotid gland, the testicle, and the ovary.

Definition. A chondroma is a tumor composed of cartilage which is the product of tissue-proliferation from a matrix of chondroblasts. This definition refers all cartilaginous tumors to a matrix composed of embryonal cartilage-cells.

Origin. It has been customary to attribute to the connective tissue under certain conditions a chondrogenetic function. It is not more likely that connective tissue can produce cartilage than that it can produce epithelial cells. In the study of the origin of tumors we must adhere closely to the teachings of Remak and Thiersch, that tissue begets tissue of its own kind. We have traced adenomata to localities where, in a normal condition, neither glands nor epithelial tissue exists, and we have to account for the presence of the tumor-matrix by the displacement of islets of adenoid tissue during the development of the embryo. We have to assign to heterotopic chondroma a similar origin by assuming as its starting-point the presence of a matrix composed of embryonic cartilage-cells or chondroblasts. Chondroma is sometimes produced by a simple outgrowth from pre-existing cartilage, that, as a rule, attains no great size. Virchow names these growths ecchondroses, and cites as their best examples outgrowths from the cartilages. of the ribs, the cartilages of the amphiarthrodial joints, the cartilages of the trachea and the bronchial tubes, and from the cartilage between the basi-sphenoid and occipital bones in the young cranium. In such

cases we must assume the existence of a superabundance of chondroblasts which produce the localized hyperplasia, but which do not result in the formation of large tumors, owing to the inhibitory influence exerted upon the growth by the surrounding normal cartilage.

In the majority of cases cartilaginous tumors are found connected with the bones and the joints. Virchow, in his classical article on "Chondroma," places great stress on the frequency with which such tumors spring from the epiphyseal cartilage. He found frequently in this locality, in adults, remnants of unossified cartilage a centimeter and more in diameter. Such islands of cartilage-tissue are frequently seen in the epiphyseal extremities of the long bones in rickety subjects.

It is well known that rickety persons are exceedingly prone to cartilaginous tumors. Virchow believes that a deficient blood-supply is often the cause of arrested ossification in such cases. The influences that excite proliferation in such embryonal remnants of cartilage are rickets and an hereditary predisposition. In glands and in other parts of the body in which normally no cartilage is found the tumor springs from a displaced matrix of chondroblasts. Förster describes two cartilaginous tumors of the lung, as large as a bean, that had undergone partial ossification. In these cases the matrix was derived from the cartilage-rings of the bronchial tubes.

Heterotopic chondroma occurs most frequently in the parotid gland and about the external ear, from tumor-cells which are derived from the cartilage of the external ear. In the vicinity of the external ear and the neck they occur as remnants of the first branchial cleft. Wartmann made a careful study of eight cases of chondroma in which the tumor developed independently of bone or cartilage. He is of the opinion that the tumor-elements start from ordinary fibrillary connective tissue, some of the fibres of which undergo hyaline degeneration; the connective-tissue fibres proliferate actively, and form groups of cells which become surrounded by a capsule and are transformed into cartilagecells. Other cells assume a stellate form; the projections form free anastomoses with similar structures which constitute a network, the intercellular hyaline substance becoming softer, forming myxomatous spaces. Both forms of cells, prior to encapsulation, present glycogen reaction, which with the perfection of the capsule disappears.

It is of course difficult to trace a tumor to its primary histogenetic origin, but it is no more difficult to explain the occurrence of chondroma in connective tissue from a displaced matrix of chondroblasts

than to explain its presence in other tissues normally devoid of cartilage-tissue, for which such an origin is generally conceded.

Histology. The structure of a chondroma depends on the kind. of cartilage it represents.

Hyaline chondroma is composed of a uniform, dense, cartilaginous mass in which islands of cartilage can be seen surrounded by ground substance. The islands of cartilage-cells are not larger than a line or a line and a half in diameter (Fig. 290). The stroma of the tumor is

FIG. 290.-Hyaline chondroma of ilium; X 130 (Surgical Clinic, Rush Medical College, Chicago): a, amorphous and granular stroma; b, cartilage-cells and capsule; c, cells in course of segmentation.

supplied with blood-vessels, but the cartilage-masses are devoid of vessels of any kind. The spaces in which the cartilage-cells are enclosed are called "lacunæ." The interior of these spaces is lined by a membranous structure from which the cells, after death, separate by shrinkage. The spaces are sometimes branched, and they have been described as "branched cells."

Fibro-chondroma.-These tumors occur most frequently in the capsule of joints and in the fibrous structures adjacent to the parotid gland. In the latter location the tumor often reaches the size of a hen's egg. The tumor resembling fibro-cartilage is not so sharply circumscribed as is the hyaline variety. The tumor-tissue consists of a uniform mass composed of fibrous tissue in the meshes of which cartilage-cells are uniformly distributed throughout (Fig. 291). The cells frequently contain oil-globules.

Reticulated Chondroma.-In this variety of chondroma the fibrous

tissue is arranged in a reticulate manner and the spaces are occupied by groups of cartilage-cells (Fig. 292). The vascular system of chondroma is imperfect. Lymphatics and nerves have not been found.

FIG. 291.-Fibro-chondroma from a cartilaginous FIG. 292-Reticulated chondroma from index finger tumor of the parotid gland (after Lücke). (after Lücke).

Retrogressive Metamorphoses.-Calcification is the most common regressive metamorphosis; it begins at circumscribed points of the

FIG. 293.-Chondroma of index finger, showing central ossification and lobulated structure of the tumor

tumor, and often terminates in the formation of large plates which are exceedingly hard and which have often been mistaken for bone. The

granules of chalk form first in the capsules and later in the cells, and deposition in the intercellular substance takes place later.

Cystic degeneration is often found in the interior of chondroma. Sometimes the tumor presents a honeycombed appearance from the presence of numerous small cysts. Coalescence of many cysts results in the formation of large irregular cavities. The softening which results in the formation of cysts is preceded by fatty degeneration of the cartilage-cells. Fat-granules appear at different points in the protoplasm of the cells, and the fatty degeneration finally terminates in the dissolution of the cells. At the same time the intercellular substance undergoes mucoid liquefaction. Hemorrhage into the cysts results in discoloration and pigmentation of the cyst-contents. If a cyst by ulceration on the surface is opened, there forms a fistulous tract which resists all treatment short of extirpation of the tumor.

Development of cartilage-cells into bone is observed in chondromata of bone and periosteum as well as in those of soft parts. Complete ossification of the tumor has never been observed. The new bone appears in the form of spiculæ representing cancellated bone (Fig. 293). The spicule of bone form septa between the cartilage-masses. Very frequently small islets of bone are found disseminated throughout the tumor.

Myxomatous degeneration is frequently observed in glandular chondroma.

Cartilaginous tumors have always been looked upon with suspicion, as they are liable to undergo transformation into sarcoma. Wartmann asserts that embolism may occur in the centre as well as in the periphery of a chondroma, and that from the emboli secondary tumors develop with the assistance of the endothelial cells of the blood-vessels, the seat of the embolic process. It is more than probable that in all cases in which a chondroma invaded adjacent tissues, and in all instances in which metastasis occurred, the tumor had undergone transition into

sarcoma.

Etiology. We have reason to assert that a chondroma cannot occur independently of the existence of a congenital matrix of chondroblasts or a post-natal matrix of embryonal cartilage-cells derived from the periosteum or the bone. O. Weber describes a case of multiple chondroma of fifteen years' duration in a man twenty-five years of age. Regarding the heredity, it has been ascertained that the grandfather, the father, the brother, and one sister were also affected with the same disease. He alludes to similar cases proving the heredity of chondroma.

Chondroma of bone occurs usually before or at

of