Omental leiomyoma in a male adult horse.

The research involves the study of a large mass found in an adult horse’s omentum at necropsy, identified as an omental leiomyoma tumor due to its physical characteristics and cell structure.

Introduction

The study describes a case of omental leiomyoma, a rare benign tumorous growth, identified in a male adult horse. This tumor was not associated with the animal’s gastrointestinal tract and was detected during a necropsy, an examination of a body after death.

Physical Properties of the Tumor

• The tumor was found in the omentum major, a large fold of visceral peritoneum that hangs down from the stomach.
• It was a well-demarcated mass measuring 70 x 35 x 28 cm and weighed 41 kg.
• The mass was comprised of multiple white-to-yellow lobules and had a hard texture.
• There were also multiple cysts found within the mass that were filled with a blood-like fluid, and some areas of the tumor were necrotic or dead tissue.

Microscopic Properties of the Tumor

• Upon histological examination, the tumor was found to be slightly pleomorphic or variably shaped, with spindloid cells arranged in intermingling bundles.
• These cells contained elongated, blunt-ended nuclei.

Immunohistochemistry

• Immunohistochemistry, a process that uses antibodies to detect the presence of specific proteins in tissues, revealed several characteristics about the tumor cells.
• Most of the tumor cells were positive for alpha-smooth muscle actin, vimentin, and neuron-specific enolase. These proteins are typically found in smooth muscle cells, indicating that the tumor originated from a muscle.
• The cells were negative for S-100, factor VIII-related antigen, and glial fibrillary acidic protein, meaning these proteins were not present in the tumor cells.
• A small number of tumor cells showed the presence of desmin and c-kit, proteins often related to muscle or connective tissue cells.

Conclusion

This study diagnosed the horse’s tumor as an omental leiomyoma, based on the macroscopic observation, histology, and immunohistochemistry results. This highlights the need for a diverse range of diagnostic tools to accurately identify and classify such rare tumors in veterinary pathology.