Horse with abnormal enlarged ovary

History of Present Illness

An 8‐year‐old Rocky Mountain Horse mare, living on pasture with other mares, was brought in for a routine yearly physical and spring reproductive status examination. The mare was not observed daily, but other mares had been seen displaying estrus behavior towards this mare. The veterinarian palpated a caudal abdominal mass on the right side, suspected to be an ovary. The left ovary was small and firm. These findings raised concern, and the mare was referred for further evaluation.