Background

The spleen is an important member of the body's immune and lymphatic system. It is located in the upper left abdominal quadrant and weighs approximately 150 grams varying for sex and age, with a gradual decrease in overall weight and size after the seventh decade. There is a thin capsule. Cross sections of the spleen reveal a red soft surface which is divided into red and white pulp. Red pulp corresponds to the sinuses which are usually filled with red blood cells. The white pulp shows white nodules, called Malpighian corpuscles. Under the microscope, these areas correspond to lymphoid follicles rich in B-cells and the periarteriolar T-cell-rich lymphoid sheaths (PALS), rich in T-cells.

The spleen is involved in most diseases that affect the other hematologic and lymphatic organs such as the bone marrow and lymph nodes. Pathologists are often called upon to evaluate a spleen for evidence of lymphoma, an important staging technique in the evaluation of lymphomas. In addition, a spleen may be removed for trauma. Rarely, there may be a solitary metastases to the organ and splenectomy may be curative.

Disorders of Red Blood Cells
Disorders of White Blood Cells
Disorders of Platelets
Hematologic-Lymphatic
Leukemia
Lymphoma
Splenic Marginal Zone Lymphoma
Splenic Sclerosing Angiomatoid Nodular Transformation (SANT)

OUTLINE

Histopathological Features and Variants
Special Stains/ Immunohistochemistry/ Electron Microscopy
Commonly Used Terms
Internet Links

HISTOLOGICAL TYPES	CHARACTERIZATION
General
VARIANTS
ACUTE SPLENITIS
Evaluation of Characteristics Associated With Acute Splenitis (Septic Spleen) as Markers of Systemic Infection James A. Feig, MD and Stephen J. Cina, MD From the Department of Pathology, Wilford Hall Medical Center, Lackland Air Force Base, Tex.	Arch Pathol Lab Med 2001;125, No. 7:888–891. Abstract quote Context.—Acute splenitis, also known as acute splenic tumor or septic spleen, is loosely defined as a neutrophilic infiltrate and congestion within the red pulp accompanied by splenomegaly. Standard pathology texts state that the histologic finding of acute splenitis is reflective of septic states. However, this association has seldom been tested in the medical literature. Objective.—The purpose of this study was to determine if sepsis can be predicted by the presence of quantitative characteristics used to identify acute splenitis. Methods.—The postmortem splenic tissue of 20 clinically diagnosed cases of sepsis and 20 noninfectious control cases were retrospectively examined in a blinded fashion for amount of neutrophilic infiltration, weight (obtained from autopsy report), and presence of congestion. Results.—No significant correlation could be found between the parameters of neutrophilic infiltrate or splenic weight and clinically diagnosed septicemia. The presence of splenic congestion was unexpectedly found to be more likely with noninfectious causes of death. Conclusion.—Acute splenitis is presently ill defined, and no available evidence convincingly shows that its presence suggests a septic state.
NEONATAL SEPSIS
Spleen depletion in neonatal sepsis and chorioamnionitis. Toti P, Felice CD, Occhini R, Schuerfeld K, Stumpo M, Epistolato MC, Vatti R, Buonocore G. Department of Human Pathology and Oncology, Siena University Hospital, University of Siena, Siena, Italy.	Am J Clin Pathol. 2004 Nov;122(5):765-71. Abstract quote   Neonatal sepsis and chorioamnionitis induce morphologic modifications and shrinkage of the thymus. We show fetal and neonatal morphologic modifications of the spleen in the same autopsy subjects as previously used to describe thymus shrinkage, including 10 preterm or full-term neonates who died of proven sepsis within 48 hours after birth and 20 fetuses spontaneously aborted because of extensive ascending chorioamnionitis. Control subjects included 10 fetuses from induced termination of pregnancy and 10 neonates who died suddenly during the perinatal period without evidence of chorioamnionitis. Spleen cell populations were studied by means of immunohistochemical analysis. Neonatal sepsis occurred with severe spleen depletion, involving both B and T lymphocytes (P < .001). Fetuses with chorioamnionitis also showed spleen cell depletion. These observations, to our knowledge not described before, indicate that preterm and term neonates show an inflammatory reaction similar to that of adult patients and that severe chorioamnionitis is associated with a nonspecific inflammatory response comparable to that of sepsis.
SCLEROSING ANGIOMATOID NODULAR TRANSFORMATION (SANT)
Sclerosing Angiomatoid Nodular Transformation (SANT): Report of 25 Cases of a Distinctive Benign Splenic Lesion. Martel M, Cheuk W, Lombardi L, Lifschitz-Mercer B, Chan JK, Rosai J. *Department of Pathology, the National Cancer Institute, Milan, Italy; daggerQueen Elizabeth Hospital, Hong Kong; and double daggerSourasky Medical Center, Tel-Aviv, Israel.	Am J Surg Pathol. 2004 Oct;28(10):1268-1279. Abstract quote   Twenty-five cases of a morphologically distinctive vascular lesion of the spleen are described. The patients were 17 women and 8 men, ranging in age from 22 to 74 years (mean, 48.4 years; median, 56 years). The most common presentations were incidental finding of an asymptomatic splenic mass (13 patients), abdominal pain or discomfort (6 patients), and splenomegaly (4 patients). None of the patients had evidence of recurrent disease after splenectomy. The splenic lesion was solitary, measuring 3 to 17 cm, and sharply demarcated from the surrounding parenchyma. The cut surface revealed a mass of coalescing red–brown nodules embedded in a dense fibrous stroma. All cases showed a remarkably consistent multinodular appearance at low-power examination. The individual nodules had an angiomatoid appearance, in the sense that they were composed of slit-like, round or irregular-shaped vascular spaces lined by plump endothelial cells and interspersed by a population of spindly or ovoid cells. Some of the nodules (particularly the smaller ones) were surrounded by concentric rings of collagen fibers. Numerous red blood cells were present, as well as scattered inflammatory cells. Nuclear atypia was minimal, mitotic figures were extremely rare, and necrosis was consistently absent. The internodular stroma consisted of variably myxoid to dense fibrous tissue with scattered plump myofibroblasts, plasma cells, lymphocytes, and siderophages. Immunostaining revealed 3 distinct types of vessels in the angiomatoid nodules: CD34+/CD8−/CD31+ capillaries, CD34−/CD8+/CD31+ sinusoids, and CD34−/CD8−/CD31+ small veins, recapitulating the composition of the normal splenic red pulp. These features are therefore different from those of littoral cell angioma, conventional hemangioma, and hemangioendothelioma of the spleen. We interpret these angiomatoid nodules as altered red pulp tissue that had been entrapped by a nonneoplastic stromal proliferative process. The characteristic morphologic appearance, immunophenotype, and benign clinical course suggest that this is a distinctive nonneoplastic vascular lesion of the spleen that we propose to designate as sclerosing angiomatoid nodular transformation (SANT).

Henry JB. Clinical Diagnosis and Management by Laboratory Methods. Twentieth Edition. WB Saunders. 2001.
Rosai J. Ackerman's Surgical Pathology. Ninth Edition. Mosby 2004.
Sternberg S. Diagnostic Surgical Pathology. Fourth Edition. Lipincott Williams and Wilkins 2004.
Robbins Pathologic Basis of Disease. Sixth Edition. WB Saunders 1999.
DeMay RM. The Art and Science of Cytopathology. Volume 1 and 2. ASCP Press. 1996.
Weedon D. Weedon's Skin Pathology Second Edition. Churchill Livingstone. 2002
Fitzpatrick's Dermatology in General Medicine. 5th Edition. McGraw-Hill. 1999.
Weiss SW and Goldblum JR. Enzinger and Weiss's Soft Tissue Tumors. Fourth Edition. Mosby 2001.

Accessory Spleen-About 10% of the population have additional smaller spleens, usually in the general area of the spleen although locations such as the testis have been described. This is important if a splenctomy is planned.

Splenosis-If traumatic rupture occurs with the spleen, the implants of splenic tissue may grow on the peritoneal surface.

Basic Principles of Disease
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Commonly Used Terms
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Diagnostic Process
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Surgical Pathology Report
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Special Stains
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How Accurate is My Report?
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Last Updated November 8, 2004

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