Fibroblast-associated protein-α expression and BPV nucleic acid distribution in equine sarcoids.
Authors: Tura Giorgia, Savini Federica, Gallina Laura, La Ragione Roberto M, Durham Andy E, Mazzeschi Martina, Lauriola Mattia, Avallone Giancarlo, Sarli Giuseppe, Brunetti Barbara, Muscatello Luisa V, Girone Cinzia, Bacci Barbara
Journal: Veterinary pathology
Summary
# Editorial Summary: Fibroblast-Associated Protein Expression and BPV Distribution in Equine Sarcoids Bovine papillomavirus (BPV) causes equine sarcoids, the most prevalent skin tumour in horses, yet the relationship between viral distribution patterns and the distinct clinical subtypes—verrucous, fibroblastic, and mixed forms—remains poorly understood. Researchers examined 74 sarcoid samples using PCR and chromogenic in situ hybridization (CISH) to map BPV localisation, alongside immunohistochemical staining for markers including fibroblast-associated protein-α (FAPα), α-smooth muscle actin, and S100 protein. BPV nucleic acid was detected in 97% of samples, predominantly with a diffuse distribution pattern (87%), though subepithelial localisation appeared more frequently in verrucous sarcoids; notably, viral signal was absent from overlying epidermis and surrounding tissue in all cases. FAPα immunolabelling was consistently positive across all sarcoid samples, identifying neoplastic fibroblasts as the primary target cells, whilst myofibroblastic differentiation (confirmed by α-SMA positivity) occurred in only 38% of cases. These findings suggest that whilst BPV distribution patterns may vary slightly between clinical subtypes, no strong correlation exists between viral localisation and histological presentation—but FAPα's universal expression offers potential as a standardised diagnostic marker for sarcoid confirmation in equine practice, which could streamline pathological diagnosis and inform future treatment approaches targeting fibroblast populations.
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Practical Takeaways
- •FAP-α immunohistochemistry may offer a new diagnostic tool for confirming sarcoid diagnosis in equine cases, potentially improving diagnostic accuracy
- •BPV appears uniformly present across different clinical sarcoid subtypes, suggesting viral activity alone does not determine clinical appearance—other factors likely influence phenotype
- •Verrucous sarcoids show a distinct subepithelial viral distribution pattern that may warrant consideration in histopathological assessment and tumor classification
Key Findings
- •BPV was detected in 97% of sarcoid samples (72/74) using PCR and/or CISH, with diffuse distribution pattern in 87% of positive cases
- •FAP-α labelling was present in neoplastic fibroblasts of all 74 sarcoids examined, suggesting it as a potential diagnostic marker
- •Subepithelial BPV distribution pattern was more frequently observed in verrucous subtype sarcoids (13% of cases)
- •No statistically significant association was found between BPV distribution patterns and clinical sarcoid subtypes or specific histological features