Granulosa Cell Tumors in Horses
Key takeaways
Granulosa cell tumors are an uncommon type of tumor in horses which arise from ovarian tissue.
- These tumors can become several times larger than the ovary and produce a number of hormonal changes in the mare, including increasing testosterone
- Symptoms include heightened aggression, irregular or absent heat cycles, crested neck, and difficulty conceiving
- Diagnostics include transrectal ultrasound, hormone testing, and biopsy of the affected ovary
- Treatment involves the full surgical removal of the affected ovary
- With surgery, the prognosis is good and the tumor has a low risk of recurrence or metastasis
- Most mares return to full reproductive function following surgery, typically within 6-8 months
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A closer look: Granulosa Cell Tumors in Horses
Granulosa cell tumors replace most of the ovarian tissue, causing hormone irregularities and reproductive issues.
Granulosa cell tumors can be fully surgically removed in most cases. With surgical removal, prognosis is good for the mare’s survival. Return to reproduction is often possible, but recovered mares might have difficulty getting in foal. Horses showing symptoms such as weakness, pale gums, and colic may have severe abdominal bleeding from a ruptured tumor. These horses require emergency veterinary attention.
Risk factors
Granulosa cell tumors are uncommon in horses, however they are the most common type of tumor of the female reproductive tract.
Granulosa cell tumors are fragile, and may rupture spontaneously causing significant blood loss into the abdomen.
The cause of granulosa cell tumors is unknown, so it is difficult to identify specific risk factors for individual horses. As with all forms of cancer, genetic and environmental factors are suspected.
Possible causes
The causes of granulosa cell tumors are not currently known.
Main symptoms
Testing and diagnosis
After a physical examination and medical history, a number of tests can be done to confirm the diagnosis;
- Transrectal ultrasound
- Biopsy of the ovary
- Hormone testing
Steps to Recovery
Treatment involves surgical removal of the affected ovary (ovariectomy). In many cases, the enlarged ovary is removed before confirming the diagnosis. After removal, laboratory submission confirms the mass as a granulosa cell tumor.
With surgical removal, the prognosis is generally good. Granulosa cell tumors are rarely metastatic and not prone to recurrence. Most mares return to normal heat cycling within 6-8 months after surgical removal of the affected ovary. Many mares are able to maintain pregnancies as normal, but may be more difficult to get in foal. Some mares do not return to normal reproductive function.
Prevention
The causes of tumor formation are not known, and therefore prevention methods are not known at this time.
Granulosa cell tumors are not contagious.
Is Granulosa Cell Tumors in Horses common?
This is the most common type of ovarian tumor in horses, but overall these tumors are uncommon.
Typical Treatment
- Ovariectomy
