Granulosa-theca cell tumors are hormonally active, sometimes large tumors found on the ovaries. They can be found incidentally on veterinary ultrasound or during palpation of a mare's reproductive tract. They also can cause abdominal pain (colic), reproductive failure, behavioral changes, and can affect performance. They usually have a characteristic appearance on ultrasound.

This diagnosis can be confirmed with a hormonal profile. Other types of ovarian tumors are much more rare, diagnosis of which require removal and submission of the tissue to a pathologist for analysis.

Talk to your vet about the options for surgical removal.