Equine granulosa cell tumours among other ovarian conditions: Diagnostic challenges.
Authors: Renaudin Catherine D, Kelleman Audrey A, Keel Kevin, McCracken Jaye L, Ball Barry A, Ferris Ryan A, McCue Patrick M, Dujovne Ghislaine, Conley Alan J
Journal: Equine veterinary journal
Summary
# Equine Granulosa Cell Tumours: Moving Beyond the Classic Presentation Whilst granulosa cell tumours (GCTs) are the most common ovarian neoplasms in mares, their diagnosis remains problematic in early or atypical cases, prompting this retrospective examination of 14 nonclassical presentations and other ovarian pathologies. The researchers documented clinical signs, endocrine profiles (including anti-Müllerian hormone [AMH], inhibin B and testosterone), and ultrasonographic findings across the case series, charting how these variables changed over time and varied between individuals. Behavioural manifestations ranged from absent to overtly stallion-like or aggressive; hormonal patterns proved erratic and unpredictable even in endocrinologically functional tumours, whilst ultrasonographic appearance evolved from initial follicular enlargement to multicystic 'honeycomb' structures—or mimicked persistent anovulatory follicles. The authors identified a helpful diagnostic benchmark: marked elevations in AMH (>10 ng/mL), inhibin B or testosterone (>100 pg/mL; 0.37 nmol/L) combined with an abnormally enlarged ovary strongly suggest GCT, whereas normal-sized ovaries with normal hormonal markers make ovarian involvement unlikely regardless of behavioural concerns. For practitioners, this work underscores that atypical GCTs demand a systematic approach integrating serial endocrine testing—particularly post-operative samples if histopathology is unavailable—rather than relying on classical signs alone, and highlights the risk of unnecessary ovariohysterectomy when normalcy across multiple diagnostic parameters persists.
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Practical Takeaways
- •Do not rely on classical presentations to diagnose GCTs; early-stage cases and non-classical presentations are common diagnostic challenges requiring careful evaluation
- •Use serum biomarkers (AMH, testosterone, inhibin B) alongside ultrasonography and palpation findings to guide ovariohysterectomy decisions, as imaging findings alone may be misleading
- •Post-surgical endocrine testing is valuable for confirming GCT removal, particularly when histopathology is unavailable or no tumour is identified during surgery
Key Findings
- •GCTs present with highly variable clinical signs ranging from no behavioural changes to aggression and stallion-like behaviour, not fitting classical descriptions
- •Hormonal profiles of endocrinologically functional GCTs can be erratic and unpredictable, with ultrasonographic appearance changing from enlarged follicles to multicystic 'honeycomb' pattern over time
- •Markedly elevated AMH (>10 ng/mL), inhibin B and/or testosterone (>100 pg/mL; 0.37 nmol/L) with abnormally enlarged ovary indicates confident GCT diagnosis
- •In mares with normal-sized ovaries, normal hormonal biomarkers, and abnormal behaviour, ovarian pathology is unlikely to be the cause