Stomach, Forestomach - Ectopic Tissue

Image of ectopic tissue in the forestomach from a female B6C3F1 mouse in a chronic study
Stomach, Forestomach - Ectopic pancreas in a female B6C3F1 mouse from a chronic study. Ectopic pancreatic acinar cells are present in the submucosa of the forestomach (arrow).
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Image of ectopic tissue in the forestomach from a female B6C3F1 mouse in a chronic study
Stomach, Forestomach - Ectopic pancreas in a female B6C3F1 mouse from a chronic study (higher magnification of Figure 1). Ectopic pancreatic acinar cells are present in the submucosa of the forestomach.
Figure 2 of 5
Image of ectopic tissue in the forestomach from a female F344/N rat in a chronic study
Stomach, Forestomach - Ectopic liver in a female F344/N rat from a chronic study. Ectopic hepatocytes (arrows) are present in the submucosa adjacent to the limiting ridge.
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Image of ectopic tissue in the forestomach from a female F344/N rat in a chronic study
Stomach, Forestomach - Ectopic liver in a female F344/N rat from a chronic study (higher magnification of Figure 3). Ectopic hepatocytes are present in the submucosa adjacent to the limiting ridge.
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Image of ectopic tissue in the forestomach from a male F344/N rat in a chronic study
Stomach, Forestomach - Ectopic intestine in a male F344/N rat from a chronic study. The submucosa is expanded by a focus of ectopic intestine with gut associated lymphoid tissue (arrow).
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comment:

Ectopic tissue can be present in the lamina propria (primarily), submucosa, or subserosa of
the forestomach. Ectopic tissue can be of any type, but pancreas ( Figure 1image opens in a pop-up window and Figure 2image opens in a pop-up window ), liver ( Figure 3image opens in a pop-up window and Figure 4image opens in a pop-up window ), and intestine ( Figure 5image opens in a pop-up window ) are common. In some cases, it can be associated with
hyperplasia of the overlying squamous epithelium. With ectopic intestine, the presence of gutassociated
lymphoid tissue should not be mistaken for inflammation. Ectopic tissue is considered an
incidental finding.

recommendation:

Whenever present, ectopic tissue should be diagnosed but not graded. The diagnosis should be modified with the tissue of origin.

references:

Bertram TA, Markovits JE, Juliana MM. 1996. Non-proliferative lesions of the alimentary canal in rats GI-1. In Guides for Toxicologic Pathology. STP/ARP/AFIP, Washington, DC, 1-16.
Full Text: https://www.toxpath.org/docs/SSNDC/GINonproliferativeRat.pdf

Frantz JD, Betton GR, Cartwright ME, Crissman JW, Macklin AW, Maronpot RR. 1991. Proliferative lesions of the non-glandular and glandular stomach in rats. GI-3. In Guides for Toxicologic Pathology. STP/ARP/AFIP, Washington, DC, 1-20.
Full Text: https://www.toxpath.org/docs/SSNDC/StomachProliferativeRat.pdf