Omental leiomyoma in a male adult horse.
Authors: Schaudien D, Müller J M V, Baumgärtner W
Journal: Veterinary pathology
Summary
# Editorial Summary: Omental Leiomyoma in a Horse A 41 kg benign smooth muscle tumour occupying the omentum majus was identified at post-mortem examination in an adult male horse, with no attachment to the gastrointestinal tract despite its substantial size (70 × 35 × 28 cm). Diagnosis relied on characteristic histopathological features—interlacing bundles of spindle cells with blunt-ended nuclei—combined with immunohistochemical confirmation showing strong positivity for alpha-smooth muscle actin and vimentin, the defining markers of smooth muscle neoplasia. Whilst large intra-abdominal masses of this magnitude would typically present with clinical signs of colic or weight loss, this case highlights that benign omental tumours may remain subclinical and go undetected until necropsy, particularly if they don't compress vital structures. The rarity of this diagnosis in equine practice means clinicians should maintain a broad differential when encountering non-responsive abdominal pain or chronic weight loss refractory to standard management, though imaging limitations in identifying omental pathology mean many such masses may never be definitively characterised ante-mortem. Understanding the behaviour of benign mesenchymal tumours in horses remains valuable for managing unexpected surgical findings and counselling owners regarding prognosis when large masses are discovered incidentally.
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Practical Takeaways
- •Omental leiomyomas are rare tumors that may not be clinically apparent until advanced stages; consider abdominal imaging in horses with nonspecific colic signs.
- •This case demonstrates that large abdominal masses can develop without obvious clinical signs, emphasizing the value of necropsy in determining cause of death.
- •While benign, the size and location of this tumor illustrates how large space-occupying lesions can develop within the abdomen without gastrointestinal obstruction.
Key Findings
- •A 41 kg omental leiomyoma was identified at necropsy in an adult male horse with no gastrointestinal tract involvement.
- •Histological examination confirmed smooth muscle origin with positive immunoreaction for alpha-smooth muscle actin, vimentin, and neuron-specific enolase.
- •The tumor displayed multiple cystic areas with blood-like fluid and multifocal necrosis despite benign classification.