Bovine Squamous Cell Carcinoma in Cattle: Etiopathogenesis, Clinicopathological Diagnosis, and Therapeutic Management

Bovine squamous cell carcinoma (SCC) is a clinically aggressive, locally destructive epithelial malignancy that inflicts substantial economic losses on livestock production worldwide. The disease manifests primarily in two distinct clinicopathological forms: Bovine Ocular Squamous Cell Carcinoma (BOSCC, or "cancer eye") in poorly pigmented Bos taurus and crossbred dairy cattle, and Bovine Horn Core Carcinoma ("horn cancer"), an occupational malignancy concentrated in castrated Bos indicus draught bullocks across the Indian subcontinent. The pathogenesis is multifactorial, driven by chronic mechanical trauma from rigid yokes, prolonged endocrine disruption following prepubertal castration, cumulative solar ultraviolet (UV) radiation, and genetic vulnerabilities including low circumocular pigmentation, Bovine Leukocyte Antigen (BoLA) haplotype variations, and TP53/MDM2 pathway dysregulation. Environmental and dietary co-factors—particularly hypovitaminosis A, antioxidant deficiencies (selenium and Vitamin E), bracken fern (Pteridium aquilinum) consumption, and bovine papillomavirus (BPV) synergism—accelerate malignant transformation. Definitive diagnosis integrates exfoliative cytology, Broders' histopathological grading (identifying pathognomonic keratin pearls and intercellular bridges), immunohistochemistry (Pan-CK, mutant p53, EGFR, and Ki-67), and PCR for viral oncoproteins. Clinical management requires early multimodal intervention, combining radical surgical extirpation (trephining horn amputation or transpalpebral orbital exenteration) with adjunctive cryoablation (-196°C), local chemotherapy (5-fluorouracil, cisplatin, and mitomycin-C), COX-2 inhibitors, and BCG immunotherapy. Because advanced cases carry a guarded to poor prognosis, long-term herd control relies on selective breeding for periocular pigmentation, early calf disbudding, improved yoke ergonomics, UV sheltering, and pasture remediation.