Tumors of the Lymphoreticular System, Including Spleen and Thymus

Christopher D.Chiliad. Fletcher MD, FRCPath , in Diagnostic Histopathology of Tumors , 2021

Patterns of Splenic Involvement in Lymphomas and Leukemias: Arroyo to Diagnosis

Equally a general rule, lymphomas tend to localize predominantly in the white pulp (with several exceptions), while leukemias tend to localize in the red pulp (with the exception of chronic lymphocytic leukemia). 1,four–vii In evaluation of lymphoproliferative lesions of the spleen, the following steps can help toward arriving at a definitive diagnosis:

1.

Weigh the spleen. A spleen weighing more than 500 one thousand nearly always harbors a significant pathologic process.

2.

Breadloaf the spleen at intervals of 2 to iii mm, and examine each slab carefully. Lesions can be pocket-sized and focal, peculiarly in early on involvement by Hodgkin lymphoma, and will be missed if the spleen is not thinly sliced.

3.

The macroscopic advent of the cut surfaces of the spleen provides a very important clue to the likely diagnosis (Table 21B.1) (Figs. 21B.ii, 21B.iii, and 21B.iv). seven Appropriate blocks should exist taken from the abnormal and the apparently normal parenchyma.

4.

Splenic hilar lymph nodes must be sampled for histologic exam. Lymphomas are sometimes easier to classify based on lymph node histology.

5.

Histologic evaluation includes determining which compartments are involved (predominantly white pulp, predominantly scarlet lurid, or both white and cherry pulp), the cellular arrangement, cytologic composition, and other histologic features. The patterns of splenic involvement by diverse types of non-Hodgkin lymphoma are listed inTabular array 21B.2. 8–13

6.

Immunohistochemical studies are invaluable for highlighting the architecture and lymphoid cell populations.

7.

In reactive atmospheric condition, such equally autoimmune disease, infection, Castleman illness, and autoimmune lymphoproliferative syndrome, the white lurid follicles can become hyperplastic, with prominent germinal centers and/or broadened marginal zones, mimicking lymphoma. one,14 Features favoring a diagnosis of lymphoma over reactive lymphoid hyperplasia include:

•

Coalescence of white pulp follicles (Fig. 21B.5)

•

Micronodular aggregates of small lymphoid cells in the red pulp that tin can be appreciated even at low magnification (run acrossFig. 21B.5A).

•

Infiltration of gristly trabeculae and subintimal layer of claret vessels (common in leukemia but less common in lymphoma) (Fig. 21B.half-dozen).

•

Immunostaining showing dense clusters or sheets of B cells in the red pulp.

eight.

The presence of many large lymphoid cells in an expanded cerise pulp tin occur in large cell lymphoma or infectious mononucleosis. The latter can fifty-fifty be associated with infiltration of the fibrous trabeculae and intima of blood vessels, heightening the mimicry of a neoplastic procedure (Fig. 21B.7). Yet, the possibility of infectious mononucleosis should always be considered for young patients. Furthermore, the large lymphoid cells in infectious mononucleosis often showroom a spectrum of appearances, with the cells apparently showing maturation into plasma cells through a plasmablastic stage.

nine.

Whenever there is unexplained sclerosis of the splenic parenchyma, the possibility of systemic mastocytosis must be seriously considered (Fig. 21B.eight).

ten.

For a detached mass lesion of the spleen showing prominent lymphoplasmacytic infiltration, EBV-positive inflammatory follicular dendritic cell sarcoma must be excluded.

Spleen

DANIEL A. ARBER , in Modern Surgical Pathology (2nd Edition), 2009

Peliosis

Peliosis of the spleen is a rare, lengthened proliferation of small vascular spaces that is usually an incidental finding in adults. 76,77 Information technology is most usually associated with prior utilise of anabolic steroids merely may also be seen in clan with malignant disease, tuberculosis, and aplastic anemia. It is frequently present in patients with hepatic peliosis. The spleen is usually non enlarged. The gross cutting surface may demonstrate small-scale (<1 mm), dilated vascular spaces or may exist unremarkable. Microscopically, numerous round to oval blood-filled cavities are present lined by a unmarried layer of flattened cells (Fig. 42-9). Prominent fibrosis of the surrounding splenic cords is not evident. In contrast to passive congestion of the spleen, which primarily involves the fundamental red pulp, peliosis involves both the key ruby-red pulp and areas immediately around the white pulp, including the marginal zone. Some cases have a distinct perifollicular blueprint of involvement. 78

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Immunohistology of Bone Marrow, Spleen, and Histiocytic Disorders

David J. Dabbs Dr. , in Diagnostic Immunohistochemistry , 2019

Normal Architecture of Spleen

The diagnostic characterization of splenic disorders tin can be all-time understood in the calorie-free of the structure and function of the spleen. 42 The spleen is composed of 2 anatomically and functionally singled-out regions. The lymphoid tissue of the spleen, calledthe white pulp, tin can be seen grossly equally uniformly distributed white nodules. The white pulp of the spleen is intimately associated with the splenic arterial/arteriolar circulation. The central arteries, which ascend from trabecular arteries within the fibrous trabeculae, are surrounded by cylindrical cuffs of lymphocytes, which are termedperiarteriolar lymphoid sheaths (PALS). The PALS comprise an admixture of B and T cells with a predominance of CD4 positive T lymphocytes (Fig. 5.viii). Periodically, splenic lymphoid follicles occur equally outgrowths of the PALS 42 and are composed predominantly of B cells that express typical pan-B cell antigens (e.g., CD20, PAX5, CD79a) (Fig. 5.9). The morphology of the splenic white pulp varies with the age of the patient and with the presence of antigenic stimulation. Inactive or hypoplastic white pulp, in which no germinal centers are seen, is characteristic of infancy, of senescence, and of the immunologically unstimulated or immunosuppressed adult spleen, with immunohistochemical features of main follicles. Every bit in lymph node, these unreacted follicles are B cells positive for IgD and BCL2, and are negative for BCL6 with a low (<5%) proliferation index past Ki67.

The reactive germinal center, is equanimous predominantly of B cells, which would express BCL6 and other germinal center markers and be negative for BCL2 with a high proliferation index by Ki67 (near 100%) (Fig. 5.ten). The marginal zone, a third layer outside the mantle zone, seen prominently in spleens, is composed of both B and T cells 42 and is the site of antigen trapping and processing. The B cells in marginal zones are positive for BCL2, negative for BCL6, and have a low proliferation index by Ki67. The marginal zone B cells express predominantly IgM with only a minor minority expressing IgD.

The red pulp of the spleen is largely composed of splenic vascular sinuses and the cords of Billroth. 42 The T cells found in the blood-red pulp are predominantly CD8-positive small lymphocytes that are rarely found in the PALS and are virtually absent-minded in the germinal centers. The ruby lurid cords contain numerous cells of monocyte/macrophage lineage, only a few of which are found in the white pulp. These express typical macrophage associated markers, including CD163 and CD68. Natural killer cells are establish scattered throughout the red pulp and inside germinal centers and are all-time highlighted by CD56 staining. The blood-red pulp besides contains granulocytes, monocytes, and lymphocytes, which pass transiently through the red pulp circulation. The sinus lining cells, likewise known every bit littoral cells, are an important functional component of the spleen. They are specialized endothelial cells with some characteristics of macrophages. Uniquely, these cells express normal vascular markers (ERG, CD31, WT1), lack CD34 expression, and limited CD8. Therefore CD8 is a useful stain in delineating the sinusoidal architecture in the spleen; even so, the extensive reactivity with CD8 tin make the evaluation of cytotoxic T cells somewhat more difficult.

Spleen

C.Due east. Grossi , P.Thousand. Lydyard , in Encyclopedia of Immunology (Second Edition), 1998

Structure of the spleen

The homo spleen is surrounded by a capsule of dumbo connective tissue containing relatively piddling musculus and therefore incapable of the all-encompassing wrinkle exhibited by the muscular capsule of the spleen in dogs and cats. A rich branching network of trabeculae from the internal capsular surface subdivides the organ into communicating compartments. The capsule is deeply indented in one part of the spleen to form the hilus where blood vessels, lymphatic vessels and nerves enter and exit. Arterial vessels co-operative into the trabeculae and from there enter the pulp or parenchyma of the organ. Veins also run in the trabeculae, inbound from the pulp. Lymphatics are constitute in the capsule and trabeculae merely not in the pulp.

The splenic lurid is supported past reticular connective tissue and is mostly red due to the presence of blood, hence carmine pulp. This is made upward by thin-walled blood vessels, the splenic sinuses (or sinusoids), and thin plates of cells which lie betwixt the sinuses, the splenic cords. Clusters of lymphocytes are grossly visible as gray-white zones surrounded past the red pulp. This is the white pulp. These lymphoid clusters are seen around arterial branches forming the PALS. The splenic pulp, at the junction between the white pulp and the ruby pulp forms the marginal zone (Figure one).

Figure 1. Organization of lymphoid tissue in the spleen. The white pulp is composed of the periarteriolar lymphatic sheaths (PALS) frequently containing germinal centers with mantle zones. The white pulp is surrounded by the marginal zone. (Marginal zones contain specialized antigen-presenting cells, macrophages and a special subset of B cells.) The red lurid contains venous sinuses separated by splenic cords. Blood enters the tissues via the trabecular artery and becomes the key artery which gives rising to many branches; some terminate in the white pulp, supplying the germinal centers and mantle zones, but most empty into or near the marginal zones. Some arterial branches run directly into the cerise lurid, mainly terminating in the cords. The venous sinuses drain blood into pulp veins and then trabecular veins. (Reproduced with permission from Roitt IM, Brostoff J and Male D (eds) (1998) Immunology, 5th edn. London: Mosby.)

At the hilus, the splenic avenue branches into trabecular arteries which leave the trabeculae and enter the PALS, where they are termed central arteries. The key artery runs out into the ruby lurid and ordinarily terminates in the cords ('open' circulation) or into the sinuses ('closed' circulation) of the red pulp. Other branches of the central artery attain the marginal zone where they open into a marginal sinus and a perimarginal cavernous sinus which bleed into venous sinuses. Veins of the pulp enter the trabeculae as trabecular veins which are continuous with the splenic vein which lies exterior the organ.

The white pulp of the spleen is lymphoid tissue consisting of lymphocytes, macrophages and other free cells lying in a reticular meshwork and surrounding arterial vessels to form the PALS (Figure 2). These are lymphoid aggregates of cylindrical form and incorporate secondary follicles with germinal centers and pall zones, similar to those establish in the lymph node cortex. The lymphoid follicles are also supplied with blood past branches of the central artery.

Effigy two. Spleen section showing the periarteriolar lymphoid sheath (PALS). This view shows the lymphoid tissue bundled around an arteriole. The T cells are found close to the fundamental arteriole and the B cell area has a germinal centre. In the 'unstimulated' state the B cell area consists of a master follicle. The lymphoid tissue is separated from the ruddy pulp past the marginal zone. This contains blood vessels and is the site of entry of bloodborne lymphocytes into the splenic lymphoid areas. H &amp; E stain, × 125. (Reproduced with permission from Roitt IM, Brostoff J and Male D (eds) (1998) Immunology, 5th edn. London: Mosby.)

The marginal zone consists of a fine meshed spongework of reticular fibers. Its cells are arranged to form a structure similar to that of the cellular cords in the cerise lurid. A marginal sinus is located directly side by side to lymphatic follicles. It consists of a series of flattened vascular spaces that lie between the white pulp and the marginal zone. A perimarginal clangorous sinus is situated outside the marginal zone or directly adjacent to the lymphoid follicles, in areas where the marginal sinus is absent.

The red pulp is a system of cellular cords lying between the venous sinuses. After distributing branches to the white lurid and marginal zone, the central artery branches into straight, slender vessels called penicilli which may stop every bit such or become finer arterial capillaries. These terminal arterial capillaries may exist surrounded past a sheath of closely packed macrophages (sheathed capillaries). A few arterial capillaries may connect with the venous sinuses, but many of them open up straight in the reticular meshwork of the cellular cords. The venous sinuses are long vascular channels with a unique endothelium and basement membrane. Endothelial cells are elongated and lie parallel to the long centrality of the vessel. They lie side by side with slit-like spaces separating them. The endothelium is perforated by large, regularly arranged, polygonal fenestrae. This organisation is traditionally likened to a barrel in which the wooden staves stand for to the endothelium and the hoops to the reticular fibers that back up the endothelial wall without a basement membrane. Sinuses are tributaries of the veins of the lurid, which in turn drain into the trabecular veins (Effigy 1).

The cellular cords are supported by a reticular meshwork. The interstices of this cordal meshwork are typically crowded with erythrocytes, macrophages, platelets, plasma cells and granulocytes. Macrophages, which differentiate from circulating monocytes, are often the predominant cells.

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The Spleen

Courtney M. Townsend JR., Doc , in Sabiston Textbook of Surgery , 2022

Surgical technique

The operation is begun with a thorough search of the abdominal crenel for the presence of accessory splenic tissue (Fig. 57.eight); the tum is retracted to the right side to facilitate examination of the gastrosplenic ligament. The splenocolic ligament, greater omentum, and phrenosplenic ligament areinspected next. The small and large bowel mesenteries, pelvis, and adnexal tissues are examined. Finally, the gastrosplenic ligament is opened, and the tail of the pancreas is confirmed to be free of splenic tissue (Fig. 57.8).

Our preference has been to use the correct lateral decubitus approach, with the operating room tabular array flexed 45 degrees from horizontal and the kidney residuum elevated. The initial dissection is begun by mobilizing the splenic flexure of the colon. Past utilise of sharp dissection, the splenocolic ligament is divided. The spleen can then be retracted cephalad; intendance should exist taken not to rupture the splenic capsule during retraction. The lateral peritoneal attachments of the spleen are incised side by side, with use of pair of scissors or ultrasonic shears. A 1-cm cuff of peritoneum is left along the lateral aspect of the spleen, which can and then be grasped to facilitate medial retraction ( Fig. 57.ix). The lesser sac is entered along the medial border of the spleen. Continuing the cephalad retraction, the curt gastric vessels and chief vascular pedicle can be identified. The tail of the pancreas is too visualized, and care is taken to avoid information technology equally it nears the splenic hilum. The short gastric vessels are divided. A number of options are currently available for this, including ultrasonic dissectors, hemoclips, bipolar devices, LigaSure (Covidien, Boulder, CO), and endovascular stapling devices. Hemoclips are used minimally around the area of the splenic hilum to prevent interference with hereafter use of a stapling device, which could pb to pregnant bleeding from improperly ligated hilar vessels.

Later on the brusque gastric vessels are divided, the splenic pedicle is carefully dissected from the medial and lateral aspects. Afterward the avenue and vein are dissected, the vessels are divided by awarding of endovascular staplers or suture ligatures. In the more prevalent distributed mode, in that location are multiple vascular branches entering the spleen close to the hilum, so the dissection is carried out approximately ii cm from the splenic capsule. Several branches may still be encountered, just these may be individually controlled more easily. A pedicle formed by the artery and vein that enters the hilum is known as the magistral blazon of arterial anatomy. If this is seen, the pedicle is transected en bloc using a linear vascular stapler. The tail of the pancreas, which is within 1 cm of the splenic hilum in 75% of patients and touches the hilum in 30%, should be well visualized as the stapler is applied to avoid injury.

The at present-devascularized spleen is suspended only from a small gage of avascular splenophrenic tissue at the superior pole. This tissue facilitates transfer of the spleen into a retrieval bag. To remove the detached spleen, the puncture-resistant nylon pocketbook is grasped by its drawstring, which can be drawn through a port, ordinarily the epigastric or supraumbilical site. The bag is opened slightly, providing access to the still intra-abdominal spleen. The spleen is and so morcellated with band forceps or finger fracture and removed piecemeal (Fig. 57.ix). In the rare cases requiring pathologic examination of an intact spleen, an incision large enough to permit extraction of the spleen must be made. Care must be taken to avoid spillage of any splenic fragments into the intestinal crenel or wound. The laparoscope is then reinserted and the splenic bed assessed for hemostasis. Drains may be placed, if necessary. Pneumoperitoneum is then released, and the fasciae of all trocar ports larger than 5 mm are closed.

Bone Marrow, Blood Cells, and the Lymphoid/Lymphatic System1

Katie M. Boes , Amy C. Durham , in Pathologic Basis of Veterinary Disease (Sixth Edition), 2017

Ruby Pulp Vascular Spaces

Storage or Defense Spleens.

Spleens are also classified as either storage or defense spleens, based on whether or non they can store pregnant volumes of blood. The ability to shop blood in the spleen depends on the fibromuscular composition of the splenic capsule and trabeculae. Splenic capsules and trabeculae with a depression percentage of shine musculus and rubberband fibers cannot expand and contract and are designated as defense spleens. These are found in rabbits and human beings. The spleens of other domestic fauna species have storage and defense functions simply are classified as storage spleens because the all-encompassing smooth musculus of the sheathing and trabeculae allows the spleen to expand and contract. The spleens of ruminants and pigs are intermediate in their corporeality of smoothen musculus and thus have express storage chapters. Equine, canine, and feline spleens all have considerable storage and contractile capacity because of their muscular capsule, increased numbers of trabeculae, and the relatively small amount of splenic parenchyma devoted to white pulp. The storage capacity in dogs and horses is remarkable: Information technology has been claimed that the canine spleen can store one-third of the dog's erythrocytes while the brute sleeps and the equine spleen holds one-half of the animate being'southward circulating red jail cell mass (which is considered advantageous considering it reduces the viscosity of the circulating blood). Storage spleens expand and contract quickly nether the influence of the autonomic nervous arrangement, via sympathetic and vagal fibers in the trabeculae and reticular walls of the red pulp vascular spaces and other circulatory disruptions, such as hypovolemic and/or cardiogenic shock. Thus storage spleens may be either grossly enlarged and congested or small with a wrinkled surface and a dry parenchyma depending on whether the spleen is congested from stored blood or shrunken from contraction (see Uniform Splenomegaly and Small Spleens).

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Molecular Footing of Lymphoid and Myeloid Diseases

Joseph R. Biggs PhD , Dong-Er Zhang PhD , in Molecular Pathology (2nd Edition), 2018

Spleen

The spleen is a lymphoid organ that as well serves equally a blood filter. The arteries of the spleen are ensheathed past lymphocytes, which form the white pulp; the white pulp is farther subdivided into a T-prison cell domain and a B-jail cell domain. The spleen, along with the lymph nodes, is a major repository for lymphocytes [5] and a major site of adaptive immune response to strange antigens [6]. The remaining internal portion of the spleen is equanimous of cerise pulp, which is designed to filter strange matter from the bloodstream, including damaged blood cells.

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Spleen Diseases

Dr. Anika Niambi Al-Shura BSc., MSOM, Ph.D , in Integrative Anatomy and Pathophysiology in TCM Cardiology, 2014

14.1 Role 1: Traditional Chinese Medicine

The spleen qi has the office of transforming food into nutrition for the production of blood, besides as keeping the blood independent in the vessels for normal apportionment. The function of the spleen qi is to transform clear fluids and send turbid fluids to the kidneys. In turn, the kidneys resend the clear through the spleen to be used past the lungs.

Copyright © 2014 Anika Niambi Al-Shura. Published by Elsevier Inc. All rights reserved.

The functions of the spleen qi are:

•

Transforming and transporting nutrition to generate qi and claret

•

Controlling blood

•

Transforming and transporting fluids

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Hematopoietic Pathology

Thomas C. Male monarch MD, PhD , in Elsevier's Integrated Pathology, 2007

SPLEEN

The spleen is a relatively mutual site for metastatic carcinoma. Splenic infarcts may mimic metastatic carcinoma. Master solid tumors of the spleen are rare and include angiosarcoma. Patients defective a functional spleen may also develop astringent disease from RBC parasites (eastward.g., malaria and babesiosis) and are at greatly increased hazard for Streptococcus pneumoniae sepsis.

Most Hodgkin'southward and not-Hodgkin's lymphomas can involve the spleen secondarily, but primary splenic lymphomas are uncommon. Primary marginal zone lymphoma of the spleen shows expansion of the marginal zone near white pulps and is usually associated with peripheral blood involvement (Fig. eleven-22). Hairy cell leukemia is a depression-grade B-prison cell neoplasm involving the spleen and bone marrow. Tumor cells have villous cytoplasmic membrane projections, giving cell borders an indistinct appearance. Hairy cells characteristically express tartrate-resistant acrid phosphatase (TRAP), which tin can be identified cytochemically on cytologic smears.

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Abdomen

S. Jacob MBBS MS (Beefcake) , in Human Anatomy, 2008

Spleen

The spleen ( Fig. 4.56) has diaphragmatic and visceral surfaces. The diaphragm separates the spleen from ribs 9–xi besides every bit the left lung and pleura.

A stab wound in the lower office of the chest wall on the left side may enter the pleural cavity before inbound the spleen through the diaphragm. The visceral surface is related to the tummy, the splenic flexure of the colon and the left kidney. An injury on the left side of the belly in its upper office may affect whatsoever of these structures. The spleen is often ruptured by blunt trauma. The hilum of the spleen is related to the tail of the pancreas, the splenic vessels and the lymph nodes. The spleen is almost completely invested by peritoneum and is continued to the breadbasket and the left kidney past gastrosplenic and lienorenal ligaments respectively.
The spleen is developed by the fusion of minor accumulation of lymphoid tissue in the dorsal mesentery. Hence it has a notch. An accessory spleen may exist present, ofttimes in the hilum of the spleen. Information technology can likewise be present wherever there is mesentery, in the omentum, small bowel mesentery or even associated with testis and ovary. See Clinical box iv.15.

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