Diagnosing atypical equine granulosa cell tumours

Misbehavior in mares is often thought to be due to ovarian tumors and the variable clinical presentations can cause confusion. Here 13 cases of atypical granulosa cell tumors are looked at and reviewed to determine what diagnostic criteria are best related to the presence of EGC tumors.
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Equine Vet J. 2020 May 11.
Equine granulosa cell tumours among other ovarian conditions: Diagnostic challenges.
Renaudin CD1, Kelleman AA2, Keel K3, McCracken JL4, Ball BA5, Ferris RA6, McCue PM6, Dujovne G1, Conley AJ1.

Author information:
1. Department of Population Health and Reproduction, School of Veterinary Medicine, University of California at Davis, Davis, California, 95616, USA.
2. Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida, 32610, USA.
3. Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California at Davis, Davis, California, 95616, USA.
4. Hagyard Equine Medical Institute, Lexington, Kentucky, 40511, USA.
5. Maxwell H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, Kentucky, 40546, USA.
6. Department of Clinical Sciences, Colorado State University, Fort Collins, Colorado, 80523, USA.
Abstract
BACKGROUND:

Granulosa Cell Tumours (GCT) are the most common ovarian tumours in mares. While the classical presentation may not represent diagnostic challenges, diagnosis is not easy in the early stages.
OBJECTIVES:

Illustrate the variability in the presentation and serum biomarkers associated with ovarian abnormalities in the mare.
STUDY DESIGN:

Retrospective case series.
METHODS:

Non-classical cases of GCTs and other ovarian conditions were identified and behaviour, GCT endocrine results, palpation and ultrasonographic findings are described and the diagnostic value of each is discussed.
RESULTS:

Mares in this case series with GCTs had presenting clinical signs ranging from no behavioural changes to behaviours including aggression, stallion-like and inability to work under saddle. Hormonal profiles of endocrinologically functional GCTs can be erratic and unpredictable. The clinical form and ultrasonographic appearance may also vary with time from an initially enlarged/anovulatory follicular structure that later develops a multi-cystic “honeycomb” appearance. Mares with GCTs can also present with persistent anovulatory follicles or apparent luteal tissue that are unresponsive to treatment. If both ovaries are of relatively normal size and symmetry, but hormonal biomarkers are markedly increased (AMH >10 ng/ml, inhibin-B and/or testosterone >100 pg/ml; 0.37 nM), it is likely that a functional GCT is present. Still, it can be a challenge to decide which ovary to remove. Post-surgical endocrine testing can be helpful, especially if histopathology is not performed or a GCT is not found.
MAIN LIMITATIONS:

Cases limited to 14.
CONCLUSIONS:

Granulosa cell tumours present with a wide variety of clinical signs that do not fit what is commonly described as “classic”. Only if AMH, testosterone and inhibin-B concentrations are markedly increased, and there is an abnormally enlarged ovary, is the diagnosis of a GCT more confident. In the presence of normal size ovaries, normal hormonal biomarkers and abnormal behaviour, it is more likely that the ovaries are not involved.