The Lymph Nodes show marked hyperplasia and enlargement, and the spleen, although enlarged, seldom reaches the size that it does in the spleno-myelogenous type.

Anemia

The nodes are softer, shrunken, and drier than normal.

Hyperemia is characterized by an increase in size of the nodes, which are reddish in color and very moist. The change is more marked in the capsular and cortical portions than in the center. It is generally the beginning stage of inflammation.

Atrophy of the nodes occurs chiefly in old age. The lymphocytes in the medullary portion degenerate, fatty metamorphosis of the connective tissue occurs, and the nodes become smaller, hard, and dry.

Hypertrophy is usually considered among the tumors as lymphadenoma.

Degenerations

Amyloid occurs in cases of general amyloid disease. The tissues first affected are the walls of the small blood-vessels and the connective tissue of the trabecule; the endothelial cells are affected later.

Hyaline changes are occasionally seen in the walls of the blood-vessels and trabeculae.

Calcification of lymph-nodes is a not infrequent end result in necrotic lesions. There may be small scattered areas of calcareous matter or a diffuse infiltration of the node.

Pigmentation may result from the presence of internal or external substances. Hemosiderin is the commonest blood-pigment. It may form as a result of local extravasation of blood, or it may be carried to the node by the blood from a hemorrhage in some adjacent tissue. The pigment-granules are found within the lymphocytes or in the cells of the stroma. The amount present may be very scanty, or so plentiful as to give a rusty color to the tissue.

External pigments, as in pneumonokoniosis in or tattooing, may find their way into the lymph-nodes, being carried there by leukocytes and other phagocytic cells. Anthracotic pigmentation is generally well marked in the bronchial lymph nodes. As a rule, the substances acting as irritants bring about a connective-tissue hyperplasia with destruction of the lymphoid tissue. Occasionally softening may result instead. If septic material is conveyed to the nodes, suppuration occurs.

Inflammation or lymphadenitis is secondary, as a rule, to the extension of inflammation following infected wounds in neighboring tissues. The infection is commonly of lymphogenic origin. The node becomes swollen, hyperemic, and tender. It may be dark red from hemorrhages. Microscopically the lymph spaces are found filled with erythrocytes, leukocytes, desquamated endothelial cells, and some fibrin. These endothelial cells frequently contain red blood cells, leukocytes, and fragments of other cells.

The process may be so severe as to bring about suppuration and abscess formation. Such a condition in the superficial nodes is termed a bubo. If deep-lying nodes are the seat of abscess formation, serious consequences may result from perforation into some internal cavity.

If the inflammation subsides during the early stage, absorption of the exudate takes place, the leukocytes pass into the circulation or break down, and the fibrin also softens. If there has been pus-formation, absorption may not take place. The pus causes hyperplasia of the neighboring connective-tissue cells, and they form a capsule. Such abscesses may calcify. At times the necrotic masses may be entirely absorbed and be replaced by a great overgrowth of connective tissue.

Chronic lymphadenitis may follow numerous acute attacks or long-continued irritation, as in tuberculosis, syphilis, and other chronic infectious diseases. There is an increase in the connective tissue, with usually atrophy or necrosis of the lymphoid structures. Calcification may follow.

Tuberculosis of the lymph-nodes may be primary, but is much more frequently secondary to disease in a neighboring structure. The specific organism is carried to the node by the lymph-channels.

In tuberculosis of the cervical nodes the tubercle bacillus gains entrance through the tonsil without causing disease at that point. The same condition may occur in the mesenteric nodes without involvement of the intestinal mucous membrane.

The tuberculous nodes are enlarged, and at first hyper-emic, although later they become paler. In the substance of the node numerous miliary tubercles may be seen, or the tissue may be represented by a broken-down caseous mass in the center. The caseation may continue until the node becomes a softened semifluid mass. The process may involve neighboring structures, and finally rupture externally, with the formation of a discharging sinus.

If the course is less acute, there may be very extensive connective-tissue hyperplasia around the disease focus, further involvement being thus prevented. Calcification may finally take place.

This variety of tuberculosis is comparatively benign. It must be remembered, however, that although a node becomes encapsulated and even calcined, it is still infectious. Though the organisms may not be recognizable microscopically, yet injection of the material into animals will usually give rise to the disease.

The microscopic appearances are the same as are found in tuberculosis in other parts of the body.

Syphilis

The lesions vary according to the stage of the disease. During the primary lesion the adjacent nodes may be the seat of an ordinary acute inflammation. They may become quite swollen and at times undergo suppuration. Such a condition is due probably to there being a mixed infection.

In the secondary stage there is a lymphadenitis in which the nodes are hard, and there is no tendency to soften and suppurate. Microscopically there is seen a round-cell infiltration, with thickening of the trabecular and proliferation of the endothelium of the lymph-spaces. The walls of the blood-vessels are thickened, and show round-cell infiltration.

In tertiary syphilis small gummata may form in the lymph-nodes, particularly in the lymph-sinuses. They are grayish, degenerated, and gummy, and are composed of leukocytes, lymphocytes, and other cells, all of which show fatty and hyaline degenerations.

Leprosy, glanders, and actinomycosis are present at times in the nodes, and show characteristic lesions.

Tumors. Leukemia

In the lymphatic form there is a general hyperplasia of the lymphatic tissues in the body. A few nodes or many may be involved, and metastatic deposits of lymphoid cells are found where normally none exist. Little change is evident; under the microscope, the enlargement is seen to result mainly from an increase of the lymph-cells without much hyperplasia of the reticulum or vessels.

The diagnosis has to be made by the changes present in the blood.

Pseudoleukemia (Hodgkiri's) disease is a condition somewhat resembling an infectious disease, and is characterized by certain changes occurring quite generally in the lymphatic tissues but starting as a rule in the cervical and axillary nodes. The appearances as described in the spleen (q. v.) are the same as occur in the lymph-nodes. The blood shows no definite changes.

Lymphoma or lymphocytoma refers to all enlargements of the lymph-nodes irrespective of the cause. The general classification includes all those conditions in which the essential change is an overgrowth of lymphocytes occurring primarily in pre-existing lymphoid tissue. May have all transitions from simple hyperplasia to a malignant cellular invasion of the surrounding tissue. The nodes are described as being of two varieties, the hard and the soft.

In the hard variety the nodes are enlarged and hard, the capsule thickened, and the trabecular increased. There is a great increase in the connective tissue and some hyperplasia of the lymph-cells.

In the soft the nodes, though enlarged, are softer and grayish. They do not suppurate. Microscopically the increase of the lymphoid tissue is the marked feature.

The enlargement of the nodes is sometimes referred to as lymphosarcoma, particularly when metastatic deposits of lymph-tissue are found in various organs, as the liver, kidneys, and heart.

Sarcoma may develop in a lymph-node, and, breaking through the capsule, involve adjacent tissues. Metastases occur in the internal organs without involving other lymph-nodes, and in that way is differentiated from lymphosarcoma. Microscopically the primary tumors may resemble each other so closely that they frequently cannot be told apart. Other forms than the round-cell, such as spindle-cell, occur.

Carcinoma, secondary in origin, is a very common condition of the lymph-nodes. It is found in those nodes that are nearest to the seat of the disease, and is due to the carrying of carcinomatous cells by the lymph-stream to the node or by a continuous growth along the lymphatics.