Metastatic extra-adrenal sympathetic paraganglioma in a horse.

This research article describes a post-mortem study of a horse that showed symptoms of colic and later died. The autopsy revealed that the horse suffered from a rare condition known as metastatic extra-adrenal sympathetic paraganglioma.

Overview of Findings

• The horse’s autopsy revealed key indicators of colic, including haemoperitoneum and a large encapsulated mass in the sublumbar area, cranial to the left kidney. This area is fairly proximal to the GI tract where colic typically presents.
• The mass was red-brown, solid, and had small nodules of matching tissue on the periphery. Additional nodules were found in the spleen and thyroid gland. This suggests a disease that had spread from the mass to other areas of the body.

Microscopic Analysis

• Upon microscopic examination, the mass, nodules near the mass, spleen, and one thyroid nodule were found to contain clusters of neoplastic cells. These cells, which indicate the presence of a tumor, were separated by a network of fine collagen and reticulin fibres.
• Further immunohistochemical analysis revealed these tumors expressed Chromogranin A, synaptophysin, and neuron-specific enolase, but not cytokeratin. Chromogranin A, synaptophysin, and neuron-specific enolase are substances often found in neuroendocrine tumors, while the absence of cytokeratin (a protein found in epithelial cells) confirms the tumor’s neuroendocrine nature.

Final Diagnosis

• Taken together, these findings were consistent with a rare condition known as metastatic extra-adrenal sympathetic paraganglioma.
• This condition is a rare form of neuroendocrine tumors that arise from specialized neural crest cells associated with the autonomic nervous system. In this case, the tumor did not originate in the adrenal glands but in a nearby area and then metastasized to other parts of the horse’s body.
• This study’s findings contribute further to the understanding of metastic extra-adrenal paraganglioma in veterinary medicine and provide clues for diagnosing such conditions in horses in the future.