Spleen - Adipocyte Metaplasia

Image of adipocyte metaplasia in the spleen from a female F344/N rat in a chronic study
Spleen - Adipocyte metaplasia in a female F344/N rat from a chronic study. Well-differentiated adipocytes (arrow) are present multifocally within the splenic red pulp.
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Image of adipocyte metaplasia in the spleen from a female F344/N rat in a chronic study
Spleen - Adipocyte metaplasia in a female F344/N rat from a chronic study (higher magnification of Figure 1). Adipocytes (arrow) are surrounded by a fibrous stroma (arrowhead).
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comment:

Adipocytes are occasionally seen in the spleen in chronic toxicity/carcinogenicity studies but may be unrelated to treatment. It has been reported in the red pulp of rats exposed to some aromatic amines (e.g., aniline, aniline hydrochloride, para-chloroaniline) and in rats with splenic mesenchymal neoplasms. This lesion is characterized by well-differentiated adipocytes in the red pulp ( Figure 1image opens in a pop-up window and Figure 2image opens in a pop-up window , arrows), surrounded by a fibrous stroma ( Figure 2image opens in a pop-up window , arrowhead), although fibrosis may not always be prominent. The red pulp is typically involved, and the lesion may be focal, nodular, and/or diffuse. These cells most likely arise by metaplasia of splenic stromal cells. Previous terms include "lipidosis," "fatty infiltration," "fatty metamorphosis," and "lipid metaplasia" of the spleen.

recommendation:

Whenever present, adipocyte metaplasia of the spleen should be diagnosed and assigned a severity grade. If this lesion is present concurrently or secondarily to neoplasia, it should not be recorded but should be described in the pathology narrative.

references:

Frith CH, Ward JM, Chandra M, Losco PE. 2000. Non-proliferative lesions of the hematopoietic system in rats. HL-1. In: Guides for Toxicologic Pathology. STP/ARP/AFIP, Washington, DC.

Goodman DG, Ward JM, Reichardt WD. 1984. Splenic fibrosis and sarcomas in F344 rats fed diets containing aniline hydrochloride, p-chloroaniline, azobenzene, o-toluidine hydrochloride, 4,4'-sulfonyldianiline, or D&C red no. 9. J Natl Cancer Inst 73:265-273.
Abstract: http://www.ncbi.nlm.nih.gov/pubmed/6588231

National Toxicology Program. 2003. NTP TR-505. Toxicology and Carcinogenesis Studies of Citral (Microencapsulated) (CAS No. 5392-40-5) in F344/N Rats and B6C3F1 Mice (Feed Studies). NTP, Research Triangle Park, NC.
Abstract: http://ntp.niehs.nih.gov/go/14888

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