A system of practical medicine. By American authors. Vol. 1

by Unknown

With the outcropping of a tumor upon a serous surface the possibility of the detachment of particles is at hand. These may become transplanted to the opposed serous surface or may be transferred to the most dependent parts, and there serve as seed for subsequent growth.

The probability of the embolic nature of many secondary tumors was early suggested in the history of embolism. Rapidly growing tumors were known to be capable of perforating the walls of adjacent blood-vessels, especially veins, and to continue growing along the course of such vessels. The possibility of the detachment of portions of these tumors and their transfer along the course of the circulation was an inevitable inference from the results of experimentation with foreign bodies. Cancerous emboli were thus recognized as a possible variety, and their distribution was subject to the same laws as those governing emboli otherwise constituted. Multiple nodules were frequently found in the lungs in connection with tumors growing into the inferior vena cava, while multiple nodules in the liver were usually associated with tumors of the gastro-intestinal canal or other regions whose vessels formed a part of the portal circulation. The readiness with which portions may be detached after death from the soft masses projecting into the interior of veins suggests the ease with which particles may be separated during life. The experiments already referred to show that isolated fragments of tissue serving as emboli may grow in the place of their reception, and it is presumable that the resulting growth takes place under the same conditions as those prevailing at the place from which the embolus started. The question whether the secondary tumor arises from the reproduction of elements transferred from the primitive disease, or whether these excite a characteristic, specific growth of the cells in the place of their retention, may still be regarded as open. The experiments favor the former view, and they alone are capable of satisfactorily determining the point in question.

The secondary nodules, whatever may be their method of origin, present the peculiarities of the primitive growth. If the cells of the latter are pigmented, those of the former show the same peculiarity. If the structure of the primitive tumor contains bone, cartilage, or squamous epithelium, the secondary growths show like characters, though they may be present in the heart or other organs where such tissues are not present as normal constituents. So constant and characteristic is this feature that the structure of the tumor is usually as well displayed in the examination of the secondary as of the primitive nodule. Indeed, the structural peculiarities of the growth may be more characteristically shown in the former in those instances where the primitive tumor has undergone degenerative changes obscuring its histological features.

The tissues of the tumor are subject to the various changes which take place in the normal tissues of the body. Their growth is attended with a multiplication of cells and a formation of intercellular substance. Tumors whose growth is the most rapid are those whose blood-vessels are the most numerous and whose relation to the cells is most intimate. The slower the advance of the tumor, the more permanent is it likely to become, while the more rapid the progress, the more transitory are its elements. The growth may continue, and yet the actual size of the tumor may diminish through the absorption of its degenerated parts. The cells of the neoplasm may undergo fatty degeneration, or they may become cornified. They may undergo the mucous metamorphosis or the amyloid and colloid degenerations. They may take up pigment or they may produce the same. The intercellular substance varies in its character as does that of normal tissues. It may be slimy, homogeneous, or fibrillated. It may contain mucin, chondrin, or gelatin, and may be infiltrated with calcareous salts. Limited necroses with characteristic cheesy appearances are of frequent occurrence.

Tumors may become the seat of inflammatory processes, indicated by suppuration and fever, which may result in abscess or gangrene, or their progress may terminate in the production of scars. Ulceration may occur in consequence of the extension of an inflammatory process to the surface, or it may result in the course of the degenerative softening of a tumor. In both cases the cutaneous or mucous surface is involved and destroyed, and the interior of the tumor being exposed putrefactive processes, with fistulæ and sinuses, arise, the latter favoring the retention of the product and the persistence of the inflammatory process.

Tumors are always pathological, but the resulting disturbances vary within wide limits and are often of a complex character. The familiar distinction between benignant and malignant tumors is based chiefly upon this variance in the nature of the disturbances. Those are benignant which closely resemble the normal structures of the body, increase but slowly, and, if they attain a large size, produce mainly mechanical disturbances. They may prove serious, even fatal, if so seated as to interfere with the function of important parts of the body. Very large and heavy tumors may prove burdensome solely on account of their weight, while others of similar character, elsewhere seated, may interfere with respiration or circulation, and eventually with nutrition. Tumors in exposed situations may become important only in virtue of their liability to injury, while others impede the function of a part or an organ by pressure upon its nerves and vessels or by obstructing its ducts.

The malignant tumors, on the contrary, differ in their structure from the normal tissues of the body. Their growth is rapid and infiltrating rather than slow and concentric. Such tumors usually have a predominance of cells and thin walled blood-vessels. The former may be little else than nuclei enveloped in an easily destructible protoplasm, or they may be composed of multi-nucleated masses of protoplasm, and are then known as giant-cells. The most malignant tumors are those which tend to become generalized as well as to spread locally. They recur locally, and appear in the nearest lymph-glands and at remote parts of the body. The disturbances produced by the malignant tumors depend less upon their mechanical relations than upon their tendency to destroy tissues and disturb functions. With their presence and progress in vital organs there is associated, from their manner of growth, a destruction of the cells of such organs, as the kidneys and liver, the lungs and heart. When they are seated in the spleen and lymphatic glands, a disturbance in the blood-making process must be associated. Their occurrence in the alimentary canal opposes the admission, digestion, and expulsion of its contents, and produces disturbances varying as to the seat and peculiarities of the tumor. The progress of the malignant tumor is often associated with ulceration, watery discharges, and hemorrhage. The frequent coexistence of emaciation, weakness, anæmia, and a yellowish discoloration of the skin forms a group of disturbances which, included under the name "cachexia," have long been prominent as significant of malignant tumors. At the present day this cachexia is regarded rather as the result than the cause of the tumor, whereas formerly the reverse was the case.

The modern classification of tumors is based chiefly on their structure, in part upon their method of origin, and in part upon their cause.

With the observation of the similarity of appearances in the flesh of which the external and internal neoplasms are composed, the suggestion readily presented itself to regard the external tumors and the internal growths as similar in character. External forms, physical characteristics, clinical peculiarities, all proved insufficient as a means of identifying the two, and the step was a short one which led to the minute study of the flesh of the tumor and a comparison of its resemblances and differences. This comparison obviously included a knowledge of the structure and peculiarities of normal tissues. As histological studies advanced, so did the pursuit of pathological histology, and the tumors which were once designated as encephaloid, mastoid, pancreatoid, or nephroid, from real or fancied resemblances to certain organs of the body, became analyzed into their microscopic rather than macroscopic characteristics.

It is unnecessary to say that the modern classification of morbid growths owes its foundation and a large part of its superstructure to Virchow, whose classic work, Die Krankhaften Geschwülste, showed the direction which future investigators were to pursue and the nature of the discoveries likely to result.