Successful intra-abdominal resection of a 24 kg ovarian granulosa cell tumor in a Warmblood mare

Abstract

Background: Granulosa cell tumors (GCTs) are the most common ovarian tumors in mares. The classical presentation
of a GCT is a unilaterally enlarged ovary appearing as a multicystic honeycomb mass. In rare cases, GCTs cause hemoperitoneum as a result of the rapid growth of the tumor. The clinical diagnosis of GCT is usually based on history,
rectal examination, ultrasonographic examination, and serum hormone analysis, and surgical removal of the affected
ovary is the treatment of choice. The different surgical approaches are based on the dimension of the GCT.
Case Description: A 7-year-old mare was referred to the department for horses due to suspicion of a large colon
impaction. The mare presented with clinical signs of colic, fever, and signs of hypovolemic shock. Rectal and
ultrasonographic examination showed hemoperitoneum and a honey-comb mass within the abdomen, and a GCT
as the cause of an acute hemoperitoneum was diagnosed based on the serum level of anti-Müllerian hormone. After
stabilization of the mare, the GCT was removed through a ventral midline incision. Because of the enormous dimensions
of the GCT, intra-abdominal partial resection of the tumor using a tenotomy knife was necessary to exteriorize the
ovarian pedicle. At 3 months follow-up, the mare was ridden for her intended use.
Conclusion: This report provides an approach to an uncommon case of a very large and heavy GCT.