Epithelioid variant of hemangioma and hemangiosarcoma in the dog, horse, and cow.
Authors: Warren A L, Summers B A
Journal: Veterinary pathology
Summary
# Epithelioid Vascular Tumours in Horses, Dogs and Cattle Endothelial tumours presenting with epithelioid cell morphology have long been recognised in human pathology but remain poorly characterised in veterinary species, making diagnosis and prognostication challenging for practitioners. Warren and Summers examined 12 vascular neoplasms (8 in dogs, 3 in horses, 1 in cattle) histologically and immunohistochemically, subdividing them into epithelioid hemangiomas (benign, n=3) and epithelioid hemangiosarcomas (malignant, n=9) based on invasiveness and metastatic behaviour; lesions occurred predominantly in dermal and subcutaneous locations, though one case involved the gastrocnemius tendon. All tumours stained positive for endothelial markers von Willebrand factor (100%) and CD31 (100%), whilst being negative for cytokeratin, definitively confirming their vascular origin rather than epithelial or histiocytic derivation. Follow-up data on half the cases revealed local recurrence in one hemangioma and two hemangiosarcomas, and regional metastasis in all three hemangiosarcoma cases with follow-up information available, highlighting the aggressive biological behaviour of the malignant variant. For equine practitioners, recognition of these tumours through appropriate immunohistochemical characterisation is essential for accurate diagnosis and client communication regarding prognosis, as their epithelioid appearance may otherwise lead to misclassification and consequently inappropriate management decisions.
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Practical Takeaways
- •Equine practitioners should be aware that epithelioid vascular tumors are rare but occur in horses; histologic confirmation with endothelial markers (von Willebrand factor, CD31) is essential for accurate diagnosis and differentiation from epithelial neoplasms
- •Hemangiosarcomas show high metastatic and recurrence potential—aggressive surgical management with wide margins and close monitoring recommended for horses with this diagnosis
- •These tumors most commonly present as dermal/subcutaneous lesions but can occur in muscle and tendon; biopsy should be considered for any unusual soft tissue masses that don't respond to standard treatment
Key Findings
- •12 epithelioid endothelial vascular tumors identified in 8 dogs, 3 horses, and 1 cow, representing a novel group with only 3 previously reported veterinary cases
- •100% of tumors positive for von Willebrand factor and CD31 (endothelial markers) and negative for cytokeratin, confirming endothelial origin
- •Of 6 animals with follow-up data, local recurrence occurred in 3 animals (1 hemangioma, 2 hemangiosarcomas) and regional metastasis in 3 animals (all hemangiosarcomas)
- •Histologic distinction between epithelioid hemangioma and hemangiosarcoma based on growth pattern invasiveness and metastatic potential