Urinary System

Kidney - Ectopic Tissue

Narrative
Comment:
In rare cases, various foci of extrarenal tissue can be noted in the kidney, particularly near the capsule. Liver tissue and adrenal tissue have been reported (Figure 1 and Figure 2). These ectopic tissues occur spontaneously with no pathologic or toxicologic significance. They must be differentiated from the presence of either primary or metastatic neoplasia.
Recommendations:
Ectopic tissues should be diagnosed when present but should not be graded. The diagnosis should be modified with the tissue of origin (e.g., Kidney - Ectopic tissue, Liver).
Related Links:
Kidney - Metaplasia, Osseous
References:

Frazier KS, Seely JC, Hard GC, Betton G, Burnett R, Nakatsuji S, Nishikawa A, Durchfeld-Meyer B, Bube A. 2012. Proliferative and non-proliferative lesions in the rat and mouse urinary system. Toxicol Pathol 40:14S-86S.

Abstract: http://www.ncbi.nlm.nih.gov/pubmed/22637735

Prentice DE, Jorgenson W. 1979. Ectopic adrenal tissue in the kidney of rhesus monkeys (Macaca mulatta). Lab Anim 13:221-223.

Full Text: http://lan.sagepub.com/content/13/3/221.full.pdf
  • Image of ectopic liver tissue in the kidney from a female F344/N rat in a chronic study

    Kidney - Ectopic tissue, Liver in a female F344/N rat from a chronic study. Ectopic liver (arrow) involves the capsule of the kidney.

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<p>Kidney - Ectopic tissue, Liver in a female F344/N rat from a chronic study. Ectopic liver (arrow) involves the capsule of the kidney.</p>

Kidney - Ectopic tissue, Liver in a female F344/N rat from a chronic study. Ectopic liver (arrow) involves the capsule of the kidney.
<p>Kidney - Ectopic tissue, Adrenal gland in a young Sprague-Dawley rat. A well-demarcated subcapsular lesion (arrow) is diagnosed as an ectopic adrenal gland. (Image provided courtesy of Dr. Johnson Thomas, Dow Chemical USA.)</p>

Kidney - Ectopic tissue, Adrenal gland in a young Sprague-Dawley rat. A well-demarcated subcapsular lesion (arrow) is diagnosed as an ectopic adrenal gland. (Image provided courtesy of Dr. Johnson Thomas, Dow Chemical USA.)

Authors 

John Curtis Seely, DVM, DACVP
Senior Pathologist
Experimental Pathology Laboratories, Inc.
Research Triangle Park, NC

Amy Brix, DVM, PhD, DACVP
Senior Pathologist
Experimental Pathology Laboratories, Inc.
Research Triangle Park, NC

Reviewers

Kendall S. Frazier, DVM, PhD, DACVP, DABT
Director, Cellular and Molecular Pathology, Safety Assessment
GlaxoSmithKline
King of Prussia, PA

Gordon C. Hard, BSc, BVSc, PhD, DSc, FRCPath, FRCVS, FAToxSci, DACVP
Expert Consultant
Tairua, New Zealand

Susan A. Elmore, MS, DVM, DACVP, DABT, FIATP
Staff Scientist, NTP Pathologist
NTP Pathology Group
National Toxicology Program
National Institute of Environmental Health Sciences
Research Triangle Park, NC