Bilateral testicle teratoma in an equine fetus: A rare case.
Authors: Nieman R T, Lamim L I, Del Fava C
Journal: Journal of equine veterinary science
Summary
# Editorial Summary Fetal loss in mares rarely stems from neoplastic conditions, and teratomas—tumours arising from partially differentiated pluripotent germ cells—have never been previously documented in equine fetal testicular tissue, despite occasional reports in cryptorchid testes of postnatal horses. Nieman and colleagues present a novel case of bilateral testicular teratoma in a 310-day-old fetus that resulted in dystocia secondary to severe abdominal distension, with diagnosis confirmed through gross and histopathological examination revealing multiple tissue types including bone, cartilage, dermis with hair follicles, and adipose and connective tissue within both affected testes. This finding broadens our understanding of neoplastic causes of fetal loss and dystocia in mares, particularly highlighting that teratomas may occur bilaterally and during fetal development rather than only manifesting as postnatal cryptorchid conditions. Clinically, practitioners managing mares with unexplained dystocia or fetal loss should maintain awareness of neoplastic differentials beyond infectious aetiologies, though the rarity of this presentation suggests it remains an uncommon consideration. The case underscores the value of thorough postmortem examination and histopathology when investigating equine reproductive losses, as recognition of such conditions may inform breeding decisions and management of affected bloodlines.
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Practical Takeaways
- •Neoplasia including teratomas should be included in differential diagnoses for dystocia cases in mares, even though these tumors are rare in equine fetuses
- •Post-mortem examination with histopathology is essential to definitively diagnose rare fetal neoplasms and contribute to understanding of equine reproductive pathology
- •Practitioners should be aware that testicular teratomas, while typically associated with cryptorchid testes in young and adult horses, can occur in developing fetuses
Key Findings
- •Bilateral testicular teratoma documented for the first time in an equine fetus at 310 days gestation
- •Histopathological examination revealed differentiated tissues including bone, cartilage, skin with hair follicles, connective tissue, and adipose tissue in both testes
- •Fetal abdominal distension from testicular enlargement resulted in dystocia requiring intervention
- •Teratomas may present with variable gross and histopathological features, complicating diagnosis