Thymic epithelial tumor with heart metastasis in a horse.
Abstract: Thymic malignancy is rare in horses. Thymic epithelial tumor was diagnosed in an 18-year-old mare with invasion and metastasis to the pericardium and heart. At necropsy, the cranial thoracic cavity was obliterated by a large mass located in the thymic region and the right atrium was also expanded and effaced by a similar mass. Histologically, the neoplasm was composed of sheets of spindle cells with intraparenchymal Hassall's corpuscles and formation of pseudorosettes around blood vessels compatible with type A thymic epithelial tumor according to World Health Organization classification. The neoplastic cells were diffusely immunoreactive for cytokeratin and negative for vimentin, S100, neuron specific enolase, glial fibrillar acidic protein, chromogranin A, synaptophysin, CD3 and CD79a markers. To the authors' knowledge, cardiac invasion and distinct histological pattern of pseudorosette formation have not been described in equine thymic epithelial tumors previously.
Publication Date: 2010-08-08 PubMed ID: 20814442PubMed Central: PMC2929616DOI: 10.4061/2010/386378Google Scholar: Lookup
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Summary
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This study reports a rare case of thymic epithelial tumor with heart metastasis in an 18-year-old female horse, describing the clinical pathology and histological characteristics of the tumor which has not been previously reported in equine medicine.
Clinical Presentation and Diagnosis
- The horse presented with a thymic epithelial tumor that had metastasized, invading the pericardium (the double-walled sac containing the heart) and heart. This is an unusual case since thymic malignancy is rarely seen in horses, and particularly the heart metastasis and specific histological pattern seen in this case have not been previously reported.
- Through necropsy, a postmortem examination to determine the cause of death, a large mass was found in the thymic region which had obliterated the cranial thoracic cavity. Additionally, a similar mass had expanded the right atrium of the horse’s heart.
Pathology and Histology
- The tumor was composed of sheets of spindle cells, which are elongated cells often seen in connective tissue tumors. These cells had developed around Hassall’s corpuscles, structures found within the thymus. Notably, the tumor also exhibited pseudorosettes around blood vessels, a formation that hadn’t been recorded in equine thymic epithelial tumors before.
- The type of tumor was recognized to be a type A thymic epithelial tumor based on the World Health Organization classification. This is one of the most common types of thymic tumors and is generally considered to have a slow growth rate and to be less aggressive than other types.
Immunohistochemistry Findings
- The neoplastic (cancerous) cells were examined for various marker proteins to better understand the type and origin of the malignancy. These cells were diffusely immunoreactive for cytokeratin, a protein found in epithelial cells, which supports the diagnosis of an epithelial tumor.
- The tumor cells tested negative for a number of other markers, including vimentin, S100, neuron specific enolase, glial fibrillar acidic protein, chromogranin A, synaptophysin, CD3 and CD79a. Negative results for these markers rule out certain types of tumors, such as those originating from nerve or immune cells.
Cite This Article
APA
Shahriar F, Moore J.
(2010).
Thymic epithelial tumor with heart metastasis in a horse.
Vet Med Int, 2010, 386378.
https://doi.org/10.4061/2010/386378 Publication
Researcher Affiliations
- California Animal Health and Food Safety Laboratory, San Bernardino Branch, University of California, Davis, 105 West Central Avenue, San Bernardino, CA 93408, USA.
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