Things are not always as they seem: an uncommon case of EcPV-7 positive laryngeal squamous cell carcinoma in a horse

Introduction A 15-year-old gelding was referred for post-mortem examination. Clinical signs during hospitalization were severe dysphagia, dyspnea, and weight loss. During endoscopic examination, marked difficulty to pass through the oropharynx was encountered. Furthermore, two sub-mandibular ulcerated fistulas draining purulent exudate were present as well as a monolateral, swollen, guttural pouch. The horse died spontaneously due to the worsening of clinical symptoms and the onset of aspiration pneumonia. Based on macroscopic appearance and anamnesis, a preliminary differential diagnosis of strangle or botryomycosis was made.

Material and methods Upon necropsy, sub-mandibular nodular skin lesions, oral mucosa, larynx, guttural pouch, sub-mandibular and retropharyngeal lymph nodes, and lung were fixed in formalin, embedded in paraffin, and stained with routine HE. Fresh samples from the larynx and the skin lesions were collected for microbiological examinations.

Results Gross pathology of the throat region extending to the sub-mandibular area revealed severe, multifocal, cutaneous, chronic abscesses with ulceration on the skin surface and fistulation in the oral cavity. Severe, monolateral, sub-acute, guttural pouch empyema was also present. Sub-mandibular and retropharyngeal lymph nodes were markedly swollen. Larynx mucosa was markedly swollen, irregular, thickened, firm, compressing and narrowing the lumen. Diffuse, moderate, acute fibrinous pleuropleumonia was also present. Histology revealed the presence of squamous cell carcinoma of the larynx. From microbiological investigation of the skin lesions Escherichia coli, Staphylococcus aureus and Roseomonas sp were isolated. Equus caballus papilloma virus type-7 (EcPV-7) was detected from the larynx while EcPV-2 was negative.

Conclusions Progression of lesions to squamous cell carcinoma (SCC) in horses is often caused by EcPV-2 that has been isolated from equine gastric, oropharyngeal, penile and vulvo-vaginal SCC. EcPV-7 has been reported to be able to cause disease mostly in association with EcPV-2. This is a rare case of laryngeal SCC with the putative cause being EcPV-7 alone.

Publikationsverlauf

Artikel online veröffentlicht:
13. Juni 2025