Metastatic esthesioneuroblastoma in a horse.

This abstract reveals the examination and diagnosis of a 17-year-old horse with a severe eye condition known as metastatic esthesioneuroblastoma. The study highlights the symptoms, post-mortem findings, and microscopic analysis to establish a final diagnosis.

Background of the Study

• The study investigated a severe eye condition in a 17-year-old horse that had developed over 1.5 years.
• The horse had exhibited a condition referred to as proptosis in the left eye, which is an abnormal bulging of the eye.
• This prompted a post-mortem examination on the horse to investigate the underlying cause of the condition.

Findings from the Post-Mortem Examination

• A neoplasm, or abnormal tissue growth, was found in various parts of the left side of the horse’s head, including the ethmoid bone, maxillary sinus, orbit, superior turbinate, and the eye.
• The tumor cells were organized in nests separated by a thin fibrovascular stroma or network of connective tissue.

Immunohistochemical Analysis

• The cells from the tumor were subjected to immunohistochemical analysis. This involves using antibodies to detect specific proteins in the cells.
• The tumor cells were found to express neurofilament protein, synaptophysin, glial fibrillary acidic protein and S-100 protein antigen. These proteins are often associated with nerve cells, suggesting the tumor originated from nervous tissue.
• The cells did not show the presence of chromogranin A, cytokeratin, and desmin, indicating the tumor was not from epithelial or muscle tissue.

Ultrastructural Findings

• Under electron microscopy, the cells revealed neurosecretory granules with an electron-dense center and a light halo, and microfilaments. These structures are characteristic of nerve cells, further confirming the nervous tissue origin of the tumor.

Concluding Diagnosis

• Based on the macroscopic, light microscopic, and ultrastructural findings, the final diagnosis was made:
• The horse had a metastatic esthesioneuroblastoma, a rare and aggressive kind of cancer that originates in the upper part of the nasal cavity and can spread to various parts of the body.