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Kidney - Ectopic Tissue

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.
Figure 1 of 2
Image of ectopic adrenal tissue in the kidney from a  Harlan Sprague-Dawley rat in a  study
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.)
Figure 2 of 2
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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 1image opens in a pop-up window and Figure 2image opens in a pop-up window ). These ectopic tissues occur spontaneously with no pathologic or toxicologic significance. They must be differentiated from the presence of either primary or metastatic neoplasia.


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).


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