Ultimobranchial body cyst in an adult horse: clinical, histopathologic, and immunohistochemical features.

The article discusses the case of a 9-year-old horse diagnosed with an ultimobranchial body cyst, a rare condition, confirmed through clinical examination, histopathologic, and immunohistochemical testing.

Case Presentation and Diagnosis

• The horse, a Mangalarga Marchador gelding, displayed symptoms including swelling on the upper right side of the neck. This prompted the referral to a veterinary hospital.
• An ultrasound exam revealed a multilocular (having multiple compartments or chambers) structure near the thyroid gland, which suggested the presence of fluid.
• The mass was surgically removed for further examination.

Histopathologic Findings

• Upon examination of the surgically removed mass, it was found that the cystic cavities were filled with an abundant amount of eosinophilic secreta, a type of immune cell.
• The lining of these cavities were covered by irregular cuboidal (cube-shaped), segmentally ciliated (having small, hair-like structures) columnar epithelium with interspersed goblet cells (cells that secrete mucus).
• Observation remarked the crowding of these layers in some portions of the cyst lining.

Immunohistochemical Findings

• Immunohistochemistry, a technique that involves tagging specific proteins with dyes to identify different cell types, was used to verify the identity of cells in the cyst.
• The cells tested positive for immunomarkers calcitonin and TTF-1, indicating the presence of C cells and follicular cells respectively, usually found in the thyroid gland.

Conclusion

• Based on all the evidence, the prefence of an ultimobranchial body cyst was confirmed. These cysts are rare and their exact cause or development (histogenesis) is uncertain.
• The conclusion holds significance as it adds to the limited body of knowledge on ultimobranchial body cysts in adult horses.