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Case Report: Histological study of gastric leiomyosarcoma in a young horse.
Abstract: During the necropsy of a 4-year-old male horse, a protruding mass was detected in the nonglandular region of the stomach. It was roughly oval in shape with a brown surface and a grayish-white cut surface. The tumor was attached to part of the stomach wall. Histologically, the tumor cells were derived from the smooth muscle layer. Tumor cells showed various morphologies and nuclear atypia. Mitotic figures were rare. Some of the tumor cells resembled smooth muscle cells. Tumor cells were seen in blood vessels within the tumor. Immunohistochemically, the tumor cells were positive for alpha smooth muscle actin antibody and were negative for CD117 (c-kit) antibody. Based on these findings, the tumor was diagnosed as leiomyosarcoma derived from gastric smooth muscle.
Copyright © 2026 Guerrero, Varela, Morales, Larrañaga, Yozzi, Yamasaki and Verdes.
Publication Date: 2026-10-21 PubMed ID: 42979435PubMed Central: PMC13730821DOI: 10.3389/fvets.2026.1979698Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
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Summary
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Overview
- A 4-year-old male horse was found to have a tumor in the nonglandular region of its stomach during necropsy.
- The tumor was identified as a leiomyosarcoma, a type of cancer originating from smooth muscle tissue in the stomach.
Detailed Explanation
Case Background
- The subject was a young, 4-year-old male horse examined postmortem (necropsy).
- During the examination, an abnormal protruding mass was discovered in the stomach’s nonglandular region, an area distinct from the glandular (secretory) stomach.
Gross (Macroscopic) Findings
- The tumor appeared roughly oval in shape.
- The surface of the tumor was brown, while the interior (cut surface) was grayish-white.
- The tumor was attached to part of the stomach wall, indicating some degree of invasion or growth from the gastric tissue.
Histological (Microscopic) Characteristics
- The tumor cells were derived from the smooth muscle layer of the stomach wall, consistent with the origin of leiomyosarcoma.
- Tumor cells showed variable shapes and structures (morphologies), as well as nuclear atypia, which means the nuclei of the tumor cells were abnormal, a hallmark of malignancy.
- Mitotic figures, indicators of cell division and tumor growth, were rare, suggesting slower division activity.
- Some tumor cells resembled normal smooth muscle cells, supporting the smooth muscle origin diagnosis.
- Tumor cells were visible within blood vessels inside the tumor, indicating local invasion and potential for metastasis.
Immunohistochemical Analysis
- Immunohistochemistry tests were performed to identify specific proteins in the tumor cells.
- Tumor cells tested positive for alpha smooth muscle actin, a protein marker characteristic of smooth muscle cells, confirming their origin.
- Tumor cells tested negative for CD117 (c-kit), a marker typically found in gastrointestinal stromal tumors (GISTs), helping to rule out other tumor types.
Diagnosis
- The combination of microscopic features and immunohistochemical profile led to the diagnosis of leiomyosarcoma, a malignant tumor originating from smooth muscle tissue in the stomach.
- This diagnosis explains the tumor’s structural and cellular characteristics as observed in the horse’s stomach.
Significance
- Gastric leiomyosarcoma is a rare tumor in horses, making this case notable.
- The identification helps better understand equine gastric tumors and potential clinical implications.
- The described methodology combining gross, microscopic, and immunohistochemical analyses illustrates the standard approach for diagnosing such tumors in veterinary pathology.
Cite This Article
APA
Guerrero H, Varela B, Morales A, Larrañaga C, Yozzi V, Yamasaki K, Verdes JM.
(2026).
Case Report: Histological study of gastric leiomyosarcoma in a young horse.
Front Vet Sci, 13, 1979698.
https://doi.org/10.3389/fvets.2026.1979698 Publication
Researcher Affiliations
- Academic Unit of Equine Medicine and Surgery, Department of Veterinary Clinics and Hospital, Faculty of Veterinary, Universidad de la República, Montevideo, Uruguay.
- Academic Unit of Pathology, Department of Pathobiology, Faculty of Veterinary, Universidad de la República, Montevideo, Uruguay.
- Academic Unit of Pathology, Department of Pathobiology, Faculty of Veterinary, Universidad de la República, Montevideo, Uruguay.
- Academic Unit of Pathology, Department of Pathobiology, Faculty of Veterinary, Universidad de la República, Montevideo, Uruguay.
- Academic Unit of Pathology, Department of Pathobiology, Faculty of Veterinary, Universidad de la República, Montevideo, Uruguay.
- Academic Unit of Pathology, Department of Pathobiology, Faculty of Veterinary, Universidad de la República, Montevideo, Uruguay.
- Academic Unit of Pathology, Department of Pathobiology, Faculty of Veterinary, Universidad de la República, Montevideo, Uruguay.
Conflict of Interest Statement
The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
References
This article includes 18 references
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