The characteristics of the growth of lymphadenoma are the involvement by continuity of all adjacent tissues, thus affording a contrast to secondary sarcomata. The glands of the neck are sometimes invaded, but are unaffected in a considerable proportion of cases. The lungs may be involved slowly, the growth following the lymphatic paths along the bronchial or vascular sheaths. The malignancy of lympho-sarcoma is unquestionable, but as a local growth it is less so than when the process is general; it is less malignant than cancer or certain forms of sarcoma.
Carcinoma of the Mediastinum.—Primary carcinoma of the mediastinum, as separated from the foregoing groups, is relatively rare; even as a secondary growth the same is true, unless it directly penetrates the chest-wall from a cancerous breast. The cancerous growths present a special peculiarity in the fact that they incorporate all the tissues with which they come in contact, and are followed by contraction. Carcinoma often originates in the lymph-tissue at the root of the lung, and may form a mass which may involve the bronchial glands, lower part of the trachea, the right and left bronchi, and surround the aorta and oesophagus. Scirrhous cancer frequently originates in the tissues at the root of the lung surrounding the bronchi and vessels, compressing them, and extending by branching rays through the lung-substance toward the periphery, following the course of the large bronchi, the lymph or arterial vessels. Carcinomatous formation may also originate in the follicles of the mucous glands of the bronchial tubes, and the mucous membrane of the same is frequently ulcerated by extension of the morbid process. The mucous membrane of the bronchi may be covered with villous-like formations springing from the surrounding growth.18 Obstruction of the bronchial lumen by carcinomatous growth may prevent the expectoration of the bronchial secretions, and dilatation of the bronchial tubes may be consecutive. These dilated tubes may become filled with pus from associated bronchitis or forms of catarrhal pneumonia.
18 See cases by Bennett and Williams, Lond. Path. Trans., vols. xix. and xxiv.; also Burrows, Med.-Chir. Trans., vol. xxvii.
The special pathological characteristics of cancerous growths are that they exist most frequently in the posterior mediastinum, and therefore exert special pressure on the respiratory passages. Again, they are subject to contraction, by which the various pulmonary structures are fused together. Hard, nodulated, cervical glands usually appear in the supra-clavicular spaces, affording special contrast in this respect with the pure sarcomata. Since, in general, the same tissues may be affected as in lympho-sarcoma or other processes affecting the bronchial glands, a positive diagnosis can usually only be made by a microscopic study of the growth. Only one lung is usually implicated, while the sarcomata spread by extension in all directions and may involve both lungs.
The effect upon the lungs of mediastinal pressure on the bronchial tubes may be very serious. Collapse of the bronchial tubes and oedema of the lungs may ensue, or subacute catarrhal inflammation with consolidation—a process which has been described by Fuchs as a form of pneumonia under the title of apneumatosis. The affected tissues not uncommonly break down by necrotic disintegration, which may lead to the formation of cavities sometimes erroneously described as resulting from softening of cancerous nodules.
Pleural effusions are prominent in the clinical history of malignant intra-thoracic disease, and especially in mediastinal processes. These effusions are consequent on pressure on the intra-thoracic circulation, or may be traceable to inflammation, either developed by irritation of the contiguous morbid process or extension of the same upon the serous membrane. Purulent pleural collections have been noted in certain cases, and they may be hemorrhagic. In 31 cases in which the character of the effusion was mentioned, 6 only were tinged with blood. This characteristic is therefore simply of relative importance. Pericardial effusion is also possible from causes similar to those operating upon the pleural tissues. Pressure may occasion dilatation or thrombosis in the vena cava. The vessels of the neck suffer, either directly from pressure inducing dilatation, or by being converted into rigid tubes, allowing of no adaptation to the amount of blood passing through them. There may be corresponding collateral swelling of the azygos or hemi-azygos veins, and at the same time collateral circulation is established between the jugular and the subclavian on the one side and the azygos and hemi-azygos on the other through the superior intercostal veins. The external thoracic veins may, in some cases, become enlarged, and infrequently compression of the inferior cava may occasion effusion into the abdominal cavity and cause oedema of the lower extremities. Morbid growths have occasionally invaded the spinal canal and excited sufficient pressure to occasion paralysis.19
19 Bennett, loc. cit.
There are certain forms of mediastinal and pulmonary tumors very seldom met with; for example, fibromata and osteomata,20 the latter sometimes occurring as an exostoses springing from the posterior surface of the sternum. Dermoid cysts of this region, as in the lungs, are also most unique. Mohr records the case of a woman æt. twenty-eight who had spat up hair since her sixteenth year. In the left lung was found a cyst which communicated with the bronchus. Inside of it was found several rounded knobs, here and there pedunculated, varying in size from a nut to a hen's egg, consisting of fibrous tissue provided with sebaceous and sweat-glands, and from which sprang numerous long hairs. The remaining contents consisted of fat and balls of hair. Teeth, bone, and cartilage can sometimes be recognized in these cysts.21
20 Die Krankhaften Geschwülste, ii. p. 102; Förster, loc. cit., p. 105; Wagner, Arch. für Physiol. Heilk., 1859, p. 411; Luschka, Virchow's Arch., Bd. x. p. 500; Förster, Ibid., Bd. xiii. p. 105; Didardier, L'Union méd., 1867, No. 83.
21 Nederland Weekblat. vor Geneesk., 1851, p. 44.