Equine Granulosa Cell Tumours

Stallion-like behaviour, crested necks and prolonged or continuous oestrous are common clinical signs mares with a Granulosa Cell Tumour (GCT) of the ovary exhibit.

These tumours usually only affect one ovary and are mostly benign in nature, but can grow to be larger than twenty centimetres in size. They produce hormones, including testosterone, which are responsible for the behavioural changes seen in affected mares. These hormones also cause the other ovary to shrink and become inactive.

Whilst most GCT’s do not metastasise, some have reported to have spread within the abdomen. The tumour itself can also cause other problems such as colic. It is therefore important to identify them, which can be achieved via a rectal ultrasound examination. There are also hormone tests available which can be helpful if the tumour is still very small.

Surgical removal of the affected ovary is the recommended treatment option. This can be performed under general anaesthesia or sometimes standing under sedation. Most horses have a significant reduction in behavioural signs and many return to normal oestrous cycling.

A twelve year old pony mare by the name of “Snort” was diagnosed with a GCT of her left ovary after her owners noticed she had started to show stallion-like behaviour.

Because of this, late last year Snort had her left ovary removed via a standing hand-assisted laparoscopic ovariectomy at Camden Equine Centre.

Snort was sedated, given an epidural and local anaesthetic injections.

A laparoscope, which is a camera that allows us to see within the abdomen through a very small incision, was inserted into her abdomen through her left flank.

The tumour was removed by using a special cutting and sealing device called a Ligasure®. The pictures below show just how big the tumour was compared to little Snort!

Because Snort did not require a general anaesthetic her recovery from the procedure was shortened and had reduced risks. She was able to go home in a few days, and in around 6 weeks was able to return to work.