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Spleen - Atrophy

Image of atrophy in the spleen from a female F344/N rat in a subchronic study
Spleen, White pulp - Atrophy in a female F344/N rat from a subchronic study. Overall area and cellularity of the white pulp (periarteriolar lymphatic sheaths and follicles) are decreased (arrows), although the marginal zones appear to be within normal limits.
Figure 1 of 4
Image of atrophy in the spleen from a female F344/N rat in a subchronic study
Spleen, White pulp - Atrophy in a female F344/N rat from a subchronic study (higher magnification of Figure 1). Decreased cellularity and area of the periarteriolar lymphatic sheath region (arrows) are evident.
Figure 2 of 4
Image of atrophy in the spleen from a female B6C3F1/N mouse in a subchronic study
Spleen - Atrophy in a female B6C3F1/N mouse from a subchronic study. Both red pulp (arrow) and white pulp (follicles, periarteriolar lymphatic sheaths, marginal zones) are atrophied.
Figure 3 of 4
Image of atrophy in the spleen from a female B6C3F1/N mouse in a subchronic study
Spleen - Atrophy in a female B6C3F1/N mouse from a subchronic study (higher magnification of Figure 3). In addition to white pulp atrophy, red pulp elements are decreased, and there is a moderate amount of pigment within the red pulp compartment (arrow).
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comment:

Atrophy can affect the white pulp and/or red pulp compartments of the spleen. Lymphocyte atrophy of the white pulp is characterized by a loss of lymphocytes in the T-cell areas (periarteriolar lymphatic sheaths [PALS]) and/or B-cell areas (follicles, germinal centers, marginal zones). Depending on severity, this can result in a decrease in overall PALS cellularity/area or follicle number/size ( Figure 1image opens in a pop-up window and Figure 2image opens in a pop-up window , arrows). Red pulp atrophy is characterized by a decrease in the relative amount of red pulp components, including hematopoietic cells ( Figure 3image opens in a pop-up window and Figure 4image opens in a pop-up window , arrows). Splenic atrophy can be observed as a spontaneous change in older rats and mice and typically involves red and white pulp compartments. Atrophy can also occur as a direct treatment-related effect or can be an indirect effect secondary to weight loss or reduced body weight gain.

recommendation:

Whenever present, atrophy of the spleen should be diagnosed and assigned a severity grade. A site modifier should be included in the diagnosis to indicate whether the red pulp or the white pulp is affected. If both compartments are involved, diagnose "Spleen - Atrophy." If splenic atrophy is present as a secondary lesion, as in the case of neoplasia, it need not be recorded but should be described in the pathology narrative.

references:

Elmore SA. 2006. Enhanced histopathology of the spleen. Toxicol Pathol 34:648-655.
Full Text: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1828535/

National Toxicology Program. 1992. 13-Week Short-Term Study of A3'-Azido-3'-Deoxythymidine (AZT) + Methadone Hydrochloride in B6C3F1 Mice (Gavage Studies) Completed (C92014). NTP, Research Triangle Park, NC.

National Toxicology Program. 2002. NTP TR-507. Toxicology and Carcinogenesis Studies of Vanadium Pentoxide (CAS No. 1314-62-1) in F344/N Rats and B6C3F1 Mice (Inhalation Studies). NTP, Research Triangle Park, NC.
Abstract: http://ntp.niehs.nih.gov/go/14892

Stefanski SA, Elwell MR, Stromberg PC. 1990. Spleen, lymph nodes, and thymus. In: Pathology of the Fischer Rat: Reference and Atlas (Boorman GA, Eustis SL, Elwell MR, Montgomery CA, MacKenzie WF, eds). Academic Press, San Diego, 369-394.

Suttie AW. 2006. Histopathology of the spleen. Toxicol Pathol 34:466-503.
Full Text: http://tpx.sagepub.com/content/34/5/466.full.pdf

Ward JM, Mann PC, Morishima H, Frith CH. 1999. Thymus, spleen, and lymph nodes. In: Pathology of the Mouse (Maronpot RR, ed). Cache River Press, Vienna, IL, 333-360.

Ward JM, Rehg JE, Morse HC III. 2012. Differentiation of rodent immune and hematopoietic system reactive lesions from neoplasias. Toxicol Pathol 40:425-434.
Abstract: http://www.ncbi.nlm.nih.gov/pubmed/22215512

NTP is located at the National Institute of Environmental Health Sciences, part of the National Institutes of Health.