Review of seven cases of granulosa cell tumour of the equine ovary.

This study examines the equine granulosa cell tumor (GCT), its clinical and pathological features, treatment, and outcomes in seven cases involving mares, which were presented with unilateral ovarian enlargement during the 2007 to 2010 breeding seasons.

Subject Description

• The mares that were part of this study were majorly characterized by unilateral ovarian enlargement.
• The age of the mares was diverse, ranging from young to mature adults with a mean age of 11.7 years. Their reproductive categories varied; three were barren, three had never given birth, and one was pregnant for the first time.
• Observations concerning the mares’ behavior were made, with 57% showing no signs of heat (anoestrus), 28% exhibiting stallion-like behaviors, and 14% consistently in heat (persistent oestrus).

Ovarian Characteristics

• All the mares had expanded one-sided ovaries. The other ovary, in each case, was small and inactive in six mares whereas the seventh, the pregnant mare, had one small corpus luteum.
• The enlarged ovaries had diameters between 7 cm and 30 cm. In terms of ultrasound appearances, 28% had multiple cysts, 57% had dense structures, and 14% had mixed appearances.

Hormonal Concentrations

• The non-pregnant mares had low progesterone levels (<1 ng/ml), moderate oestrone sulphate (3.06 ng/ml), and testosterone levels (0.58 nmol/l), but their inhibin was high at 7.6 ng/ml.
• The pregnant mare had higher hormonal concentrations with progesterone at 2.5 ng/ml, oestrone sulphate at 81.0 ng/ml, testosterone at 1.9 nmol/l, and inhibin at 1.31 ng/ml
• Mares that displayed stallion-like behavior had significantly higher concentrations of testosterone than mares that did not.

Treatment and Outcome

• Three of the mares underwent a surgery called a unilateral ovariectomy to remove the enlarged ovary.
• The operation did not negatively impact their overall reproductive capabilities, as all mares resumed cyclical ovarian activity within nine months of surgery.