Mesenchymal hamartoma of the liver in a late-term equine fetus.
Authors: Brown D L, Anderson M, Cullen J M
Journal: Veterinary pathology
Summary
# Editorial Summary: Mesenchymal Hamartoma of the Liver in an Equine Fetus Mesenchymal hamartoma represents a rare congenital developmental abnormality affecting biliary tract organisation, with very limited documentation in equine medicine. Brown and colleagues examined a late-term equine fetus during necropsy and identified a dramatically enlarged liver—more than double normal weight—with hepatic parenchyma completely replaced by abnormal bile duct proliferation embedded within abundant myxoid stromal tissue. Histopathological analysis revealed the characteristic features of mesenchymal hamartoma, alongside areas of fibrotic bridging and small-calibre bile duct proliferations consistent with congenital hepatic fibrosis. Although this condition is incompatible with postnatal life and therefore represents a prenatal pathological finding rather than a clinical management concern, recognition of these lesions contributes to understanding congenital biliary developmental disorders in horses and may inform diagnostic interpretation in affected pregnancies. Equine practitioners encountering unexplained fetal loss or hepatic abnormalities on imaging should be aware that mesenchymal hamartoma, whilst exceptionally rare, falls within the differential diagnosis of congenital liver disease in this species.
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Practical Takeaways
- •This is an extremely rare congenital condition with limited clinical relevance to most equine practitioners; recognition may be important only in cases of fetal loss with unexplained hepatomegaly
- •Pathological diagnosis requires histopathological examination and cannot be made on gross appearance alone
- •No practical management or prevention strategies are derivable from this single case report
Key Findings
- •Mesenchymal hamartoma presented as markedly enlarged liver (>2× normal weight) in late-term equine fetus
- •Histopathology revealed obliteration of normal hepatic parenchyma replaced by abnormal bile ducts within myxoid stroma
- •Lesion contained bridging fibrosis septa and proliferations of small-caliber abnormal bile ducts resembling congenital hepatic fibrosis