Cytokeratin AE1/AE3 immunolabeling in epithelioid hemangiosarcoma.
Authors: Barrantes Murillo Daniel Felipe, Negrão Watanabe Tatiane Terumi, Wiener Dominique J, Miller Andrew, Rissi Daniel R, Sandey Maninder
Journal: Veterinary pathology
Summary
# Editorial Summary: Cytokeratin Immunolabeling in Epithelioid Hemangiosarcoma Epithelioid hemangiosarcoma represents a diagnostically challenging vascular tumour variant that mimics epithelial neoplasms due to its pleomorphic cell morphology and arrangement in cord-like or solid patterns. Researchers from five veterinary institutions examined cytokeratin AE1/AE3 (CK AE1/AE3) immunostaining across 30 canine cases using immunohistochemistry for both the endothelial marker CD31 and cytokeratin, reflecting diagnostic protocols used in human pathology. Cytokeratin immunolabeling was identified in 43% of cases (13/30), with cytoplasmic positivity ranging from 5–100% of tumour cells, mirroring the approximately 50% positivity rate reported in human epithelioid hemangiosarcomas. All tumours demonstrated consistent membranous CD31 immunostaining, confirming vascular origin despite the misleading epithelial appearance. When evaluating cutaneous or subcutaneous incisional biopsies suspected of epithelioid hemangiosarcoma, practitioners and pathologists should insist on concurrent vascular marker immunostaining (particularly CD31) alongside routine cytokeratin studies to avoid misclassification as carcinoma and ensure appropriate prognostic and therapeutic planning.
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Practical Takeaways
- •When epithelioid hemangiosarcoma is suspected, especially in small cutaneous or subcutaneous biopsies, always include vascular markers like CD31 in immunohistochemistry panels to avoid misdiagnosis as carcinoma
- •Cytokeratin positivity does not rule out hemangiosarcoma; vascular markers are essential for accurate diagnosis
- •This study applies to small animal (canine) pathology—relevance to equine practice is limited as the study focuses on dogs
Key Findings
- •Cytokeratin AE1/AE3 immunolabeling was detected in 43% (13/30) of canine epithelioid hemangiosarcoma cases, with labeling ranging from 5% to 100% of neoplastic cells
- •All 30 tumors consistently showed membranous CD31 immunolabeling, confirming vascular origin
- •CK AE1/AE3 immunolabeling pattern in canine epithelioid hemangiosarcomas resembles that in humans, creating similar diagnostic challenges in distinguishing from carcinomas