Alimentary System

Stomach, Forestomach - Ectopic Tissue

Narrative
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 1 and Figure 2), liver (Figure 3 and Figure 4), and intestine (Figure 5) are common. In some cases, it can be associated with hyperplasia of the overlying squamous epithelium. With ectopic intestine, the presence of gut-associated lymphoid tissue should not be mistaken for inflammation. Ectopic tissue is considered an incidental finding.
Recommendations:
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
  • 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).

Enlarge Image
Enlarge All Images
<p>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).</p>

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).
<p>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.</p>

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.
<p>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.</p>

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.
<p>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.</p>

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.
<p>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).</p>

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).

Authors:

Linda H. Kooistra, DVM, PhD, DACVP
Pathologist
Charles River Laboratories, Inc.
Research Triangle Park, NC

Abraham Nyska, DVM, Diplomate ECVP, Fellow IATP
Expert in Toxicologic Pathology
Visiting Full Professor of Pathology
Sackler School of Medicine, Tel Aviv University Timrat Israel

Reviewers:

Joel R. Leininger, DVM, PhD
Senior Pathologist
MedImmune
Washington, DC

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