Orbital neuroendocrine tumors in three horses.

The study reports the occurrence of orbital neuroendocrine tumors in three horses, and how these presented as a mass in their orbital area (the area around the eyes). The researchers adopted various methods for the evaluation of these tumors, and compared them to similar ones found in humans.

Context and Purpose

• The three horses under study were reported to exhibit exophthalmos (the protrusion of the eyeball from the orbit) as well as other signs indicative of an orbital mass.
• The primary goal of the study was to identify and understand the cause of these symptoms, and subsequently carry out the appropriate treatment.

Methodology and Findings

• The researchers performed exenteration (removal of the contents of the animal’s eye socket) in two out of three horses to physically get rid of the problematic mass.
• In the third horse, during necropsy (an autopsy for animals), it was discovered that there was also an orbital tumor and lung metastases (spread of the tumor cells).
• Various lab tests, such as histologic staining, Grimelius’ histochemical staining, immunohistochemical staining for chromogranin, and electron microscopy, were implemented on the extracted fixed tissues to understand the characteristics, structure, and behavior of the tumors.
• The masses were determined to be orbital neuroendocrine tumors which are a type of tumor that arises from the neuroendocrine system.
• The horses that underwent exenteration survived 19 to 24 months post-surgery.
• It was noted that both these horses experienced hypotension (low blood pressure) during the surgery which the researchers imply may have resulted from the manipulation of the tumor.

Comparative Aspect

• It is reported that the orbital neuroendocrine tumors found in these horses bear close resemblance to the orbital paragangliomas that are rarely found in human beings.
• This comparative angle suggests the researchers’ intention to inform both veterinary and human medical practices, as well as provides a basis for future research in this direction.