Background

This case report describes an uncommon presentation of invasive aspergillosis in a young, otherwise healthy cat. While Aspergillus infections are known to cause localized sinonasal or disseminated disease in cats, invasive tracheal or mediastinal involvement is rare and typically occurs in immunocompromised patients. The report highlights the potential for severe, life-threatening aspergillosis to occur in immunocompetent cats.

Methods

A 3.5-year-old castrated male domestic medium-hair cat was evaluated for a 10-day history of coughing, labored breathing, and a cranial mediastinal mass detected radiographically. Diagnostic workup included computed tomography (CT), fine-needle aspiration, and later surgical exploration. Necropsy and histopathology were performed following euthanasia. Fungal culture and PCR sequencing were used to identify the etiologic agent.

Results

CT imaging revealed a large cranial mediastinal mass compressing the trachea and major thoracic vessels, with differential diagnoses including neoplasia and granuloma. Surgical findings showed extensive adherence of the mass to the cranial vena cava, aortic arch, and brachiocephalic trunk, precluding safe resection. Necropsy confirmed tracheal wall invasion and fungal plaques within the lumen. Histopathology identified a fibrosing fungal granuloma with hyphal and pseudohyphal elements. Culture and panfungal PCR confirmed Aspergillus lentulus infection, with sequence identity >99%. No disseminated lesions were detected.

Limitations

As a single case report, the findings cannot determine prevalence or causation. The absence of definitive invasion on preoperative imaging limited diagnostic certainty. Lack of therapeutic intervention data prevents assessment of antifungal treatment efficacy in similar cases.

Conclusions

This report documents a rare instance of invasive tracheal and mediastinal Aspergillus lentulus infection in a young, immunocompetent cat. The case underscores the diagnostic difficulty of identifying invasive fungal disease on imaging and emphasizes that invasive aspergillosis should be considered in the differential diagnosis for cranial mediastinal masses, even in healthy feline patients. The prognosis remains poor when resection is not feasible.

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