Review of seven cases of granulosa cell tumour of the equine ovary.
Authors: Crabtree J
Journal: The Veterinary record
Summary
Granulosa cell tumours (GCTs) represent a significant differential diagnosis in mares presenting with unilateral ovarian enlargement and reproductive dysfunction, though their clinical manifestations are variable and potentially confusing. Crabtree's review of seven cases documented the clinicopathological features across animals aged 7–22 years, with tumours ranging from 7–30 cm in diameter and exhibiting diverse ultrasound appearances (multicystic, dense, or mixed). Hormonal profiling revealed the diagnostic utility of elevated inhibin (mean 7.6 ng/ml in affected mares) combined with suppressed progesterone (<1 ng/ml) in non-pregnant animals, whilst testosterone concentrations correlated directly with behavioural presentation—mares exhibiting stallion-like behaviour had significantly higher testosterone (mean 1.85 nmol/l) than those without such signs. Three mares treated with unilateral ovariectomy successfully resumed cyclic activity within nine months, indicating that surgical removal of the tumour-bearing ovary can restore reproductive function despite the advanced age of some animals. For practitioners managing chronic anoestrus, persistent oestrus, or unexplained behavioural changes in mares with sonographically abnormal ovaries, GCT warrants serious consideration and hormone analysis—particularly inhibin measurement—should guide diagnostic and surgical decision-making.
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Practical Takeaways
- •Granulosa cell tumours should be suspected in older mares (mean age 11.7 years) presenting with unilateral ovarian enlargement and abnormal reproductive behaviour including anoestrus, stallion-like behaviour, or persistent oestrus
- •Elevated inhibin and testosterone concentrations with suppressed progesterone support GCT diagnosis and help differentiate from other ovarian pathologies
- •Unilateral ovariectomy offers a successful treatment option, with most mares resuming normal cyclic activity within 9 months, making early diagnosis and surgical intervention worthwhile
Key Findings
- •Mean age of affected mares was 11.7 years with unilateral ovarian enlargement ranging from 7 to 30 cm in diameter
- •Elevated inhibin concentrations (7.6 ng/ml) and low progesterone (<1 ng/ml) were consistent findings in non-pregnant mares with GCT
- •Mares with stallion-like behaviour had significantly higher testosterone concentrations (1.85 nmol/l) compared to those without (0.34 nmol/l, P<0.001)
- •Three mares undergoing unilateral ovariectomy resumed cyclic ovarian activity within nine months post-surgery