We describe 12 epithelioid endothelial vascular tumors in 8 dogs, 3 horses, and 1 cow that share microscopic features with these tumors in humans.
Ten tumors were located within the dermis and subcutis, 1 in the gastrocnemius tendon, and 1 in the skeletal muscle of the thigh.
Key histologic features were the plump, epithelioid appearance of neoplastic endothelial cells and occasional cytoplasmic vacuolation, which rarely contained a single erythrocyte.
Patterns of epithelioid endothelial cell growth ranged from conventional vasoformative structures to glandlike acini and short ducts to solid, sheetlike arrangements.
All tumors were positive for endothelial markers: 12/12 (100%) were positive for von Willebrand factor with variable intensity and distribution and 9/9 (100%) were positive for CD31. All 12 were negative for cytokeratin.
We subdivided these tumors into epithelioid hemangiomas (n = 3) and hemangiosarcomas (n = 9) based on conventional morphologic criteria, growth pattern (invasive or not), and metastasis (known in 1 case at the time of biopsy).
Additional follow-up information obtained by a written questionnaire was available for 6/12 (50%) animals and revealed local recurrence in 3 animals (1 epithelioid hemangioma and 2 epithelioid hemangiosarcoma) and regional metastasis in 3 animals (all epithelioid hemangiosarcomas).
This series represents a novel group of vascular tumors in domestic animals of which there are only 3 previous cases reported in the veterinary literature.
Source: A. L. Warren and B. A. Summers (2007): Epithelioid Variant of Hemangioma and Hemangiosarcoma in the Dog, Horse, and Cow. In: Vet Pathol 44:15-24 (2007)
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