This section is from the book "A Manual Of Pathology", by Guthrie McConnell. Also available from Amazon: A Manual Of Pathology.
Total absence may occur. It may be divided into lobes, and accessory or supernumerary spleens of small size are quite common.
The organ may be unusually movable. It may be much displaced by pressure from neighboring organs or collections of fluids.
Anemia may be part of a general condition or follow severe hemorrhage. The organ is smaller than normal, pale, and the capsule is much wrinkled. On section, the stroma is prominent and the color is a reddish-gray or slate.
Active hyperemia is physiologic after a large meal, and is almost constantly present in the infectious fevers. The spleen may be several times its normal size, is dark red in color, and the capsule is greatly stretched and the pulp so very soft, almost semifluid, that it oozes from the cut surface. If the condition is acute, the swelling is due to the hyperemia. If long continued, the connective tissue may increase in both the trabeculae and the capsule.
This active hyperemia is especially common in typhoid fever, and the micro-organisms can usually be recovered from the spleen.
Passive hyperemia is due to obstruction of the circulation, as in cirrhosis of the liver and chronic heart and lung diseases. The condition is known as cyanotic induration, on account of the characteristic color and firmness. The spleen is larger and bluish-red in color; the capsule is tense, and the pulp soft. As the condition persists, there is an increase in the connective-tissue of the capsule and the trabeculae. There may be finally an atrophy of the splenic pulp, with contraction of the fibrous tissue, so that the organ becomes smaller, firmer, and somewhat distorted.
Hemorrhage is usually the result of traumatism, and occurs beneath the capsule. It may occur spontaneously in certain forms of disease, as typhoid fever and malaria. A common form is that which occurs in hemorrhage infarction as a consequence of embolism. The conic area has its base toward the periphery and the apex toward the hilum. The infarcts may be small or large, single or multiple. It rapidly breaks down, and if micro-organisms are present, an abscess may form. Otherwise the detritus is gradually absorbed and replaced by fibrous tissue which forms an irregular, contracted scar in which there is frequently more or less pigment.
Embolism is quite common and causes either hemorrhagic or anemic infarcts. The anemic is similar to the above, except that it is paler on account of containing less blood.
Thrombosis of the splenic vein is generally secondary to a similar condition of the portal vein.
Splenic tumor is the term applied to the enlargement that occurs in infectious diseases. The spleen may be three to four times the normal bulk, dark colored, red or reddish-black, and very soft; the capsule is stretched; the trabecular and the Malpighian bodies are invisible on section, and the tissue is very friable and mushy. Microscopically the vessels are dilated and the pulp is composed of great numbers of lymphocytes and polymorphonuclear leukocytes. Many large mononuclear cells containing erythrocytes are present. Mitotic figures are frequently found in them. Small areas of focal necrosis are also frequently present.
The enlargement of the spleen subsides as the disease declines, but it seldom gets quite as small as before the attack, on account of the fibrous overgrowth that occurs.
Acute splenitis is usually of a suppurative character, due usually to hematogenous infection, in the form of septic emboli. Abscesses, either single or multiple, form. They may be absorbed or may rupture into some neighboring cavity, as the peritoneal, or into the stomach, intestine, lung, or pleura.
Chronic splenitis is generally diffuse, and is characterized by a great hyperplasia of the connective tissue. In its most marked form it occurs in chronic malaria. It may also occur in either congenital or acquired syphilis, in prolonged typhoid fever, and in leukemia and pseudoleukemia.
The spleen is at first enlarged, but becomes smaller as the process continues. The capsule is stretched and much thickened, and may contain circumscribed areas that are almost cartilaginous in their density. The trabecular are also thickened. The organ is then quite firm, and may be dark in color on account of the presence of pigment.
Microscopically there is a hyperplasia of both pulp and interstitial tissue.
Perisplenitis is an inflammation of the capsule of the spleen usually resulting in the production of an increased amount of connective tissue. The capsule becomes much thickened over a considerable area and adhesions may form between it and adjacent structures.
Tuberculosis of the spleen is rare as a primary affection, but is quite frequent as a secondary condition, and appears as a miliary infection. The tubercles are small grayish spots, not unlike the Malpighian corpuscles. They undergo a central caseation. At times the tubercles may be as large as a pea but not as numerous as in the miliary type.
Syphilis is very rare, but occurs in the form of gummata. They are generally multiple, and at first grayish, later becoming yellowish on account of degeneration in the central part of the node. There may also be a diffuse increase of the connective tissue.
Atrophy of the spleen is very common in old age. The capsule is wrinkled and thickened, and the organ is pale, flabby, and pigmented, and there is an increase in the stroma. Circumscribed areas in the capsule of extreme thickness and cartilaginous density may be present and be the cause of atrophy.
Amyloid disease affects the spleen more frequently than any other organ. It makes its appearance in the walls of the blood-vessels in the Malpighian bodies, and involves the adjacent connective-tissue, with atrophy and at times disappearance of the lymphoid cells. The bodies become enlarged, pale, and translucent, resembling boiled sago, hence it is known as the sago spleen. Such a spleen is generally about normal in size. Occasionally the degeneration may be more diffuse, affecting the connective-tissue stroma. The organ may be greatly enlarged. The cut surface is dry, translucent, firm, and friable, and is about the same color as dried beef. The edges also are rounded. The degenerated areas give a mahogany-brown color on the addition of iodin.
Fig. 181. - Amyloid Degeneration of the Spleen (Sago Spleen).
X 24 (Dürck).
1, An amyloid follicle, in which are seen only a few nuclei; the bloodvessels, in transverse section, have also undergone amyloid degeneration; 2, compressed pulp-spaces; 3, trabecular.
Pigmentation of the spleen is found in chronic congestion, as in cirrhosis of the liver and in malaria. Hemolysis takes place, and the freed pigment is found in the walls of the bloodvessels and in the parenchyma cells. In malaria the pigment is melanin, in other conditions hemosiderin. External pigment, as coal-dust, may lodge in the spleen. It gains entrance into a blood-vessel by erosion from pressure of an anthracotic lymph-node.
Calcification is found occasionally in old infarcts, in a thickened capsule, and in degenerated areas of tuberculosis and syphilis.
The spleen becomes greatly enlarged, weighing at times as much as 5 to 10 kilograms. The capsule is much thickened. In the early stage the organ is enlarged and soft, but finally becomes firm and dense, on account of the hyperplasia of the lymphoid tissue. On section, the spleen is seen to be very much congested, and the Malpighian bodies appear quite prominent.
There is anemia resulting from pressure of the capsule on the pulp; many of the cells degenerate, and both anemic and hemorrhagic infarcts may occur. On section, the cut surface is found to be very mottled. Reddish areas, small yellowish necrotic masses, whitish bodies of lymphoid tissue, and infarctions may all be present. Microscopically the Malpighian corpuscles are found much enlarged, and contain cells showing mitoses. The new cells may be larger than normal, and giant-cells are occasionally seen. The pulp is congested and degenerated, containing pigment and large phagocytic cells in which are found erythrocytes and detritus.
The changes in lymphoid and myelogenous leukemia are very much alike except that in the latter many myelocytes are present and the spleen is larger.
Tuberculosis is not infrequently present at the same time as leukemia, and may modify the general appearances.
The gross appearances are practically the same as in leukemia, but there are differences in the microscopic picture. "In the spleen and lymph-nodes there is hyperplasia of the lymphoid tissue, proliferation of the reticular endothelial cells, formation of uninuclear and multi-nuclear giant-cells, thickening of the reticulum, and final overgrowth of connective tissue. Eosinophiles, though not specific, are frequently found in great abundance. There is also an increase in the eosinophilic leukocytes and myelocytes of the bone-marrow".
The spleen shows a general hyperplasia of connective tissue of varying degree, involving the capsule, the reticulum of the pulp, and in particular the Malpighian bodies. These latter may show hyaline changes. The blood spaces in many cases show more or less hyperplasia of the lining endothelial cells. Sometimes this proliferation may be so extensive as to suggest true tumor formation. (Gaucher type.) Areas of hemorrhage, infarcts, and perisplenic adhesions are occasionally found.
In the terminal stage of splenic anemia the liver may show a more or less marked degree of portal cirrhosis (Band's disease).
Primary growths are rare. Secondary sarcoma and carcinoma are sometimes found in generalized metastases.
Cysts are rare. Small ones may be due to degeneration of a follicle. Large ones are occasionally found.
Parasites are also rare, but the Pentastomum denticulatum, the cysticercus, and the Taenia echinococcus have all been described, the last the most frequently.