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Published on: September 13, 2019
Embryonal rhabdomyosarcoma in an immature Baird's tapir (Tapirus bairdii)
Christopher J Bonar1, Albert H Lewandowski, Anthony J Skowronek
1Cleveland Metroparks Zoo, Ohio 44109, USA.
Abstract:
An immature Baird's tapir (Tapirus bairdii) with a history of seizure-like episodes developed signs of respiratory disease. The initial clinical diagnosis was pneumonia, and antibiotic therapy was started. The animal failed to improve after 14 days of therapy and developed unilateral, bloody nasal discharge. Endoscopic examination and radiography revealed a soft tissue mass in the nasopharynx depressing the soft palate. The tapir died 32 days after initial presentation. Histologic examination of the mass demonstrated a mesenchymal tumor composed of spindle cells with elongate nuclei forming densely packed fascicles. The neoplastic spindle cells showed prominent cross-striations. Immunohistochemistry revealed the cells to be positive for desmin and myoglobin, but negative for smooth muscle actin, confirming diagnosis of rhabdomyosarcoma. Embryonal rhabdomyosarcoma is the most common nasopharyngeal soft tissue tumor of humans, and it has been reported infrequently in dogs, horses, and pigs. Neoplasia should be a differential diagnosis in cases of unilateral nasal discharge and inspiratory stridor, even in young animals.
Insights
A rare rhabdomyosarcoma tumor was diagnosed in an immature Baird's tapir (Tapirus bairdii) presenting with respiratory disease and nasal discharge. This finding highlights neoplasia as a key differential diagnosis in similar cases.
Area of Science:
- Veterinary Pathology
- Comparative Oncology
- Wildlife Health
Background:
- Baird's tapirs (Tapirus bairdii) are endangered megafauna with limited published data on neoplastic diseases.
- Respiratory and nasal conditions in tapirs are often presumed to be infectious, delaying diagnosis of other etiologies.
Observation:
- An immature Baird's tapir presented with seizure-like episodes, progressing to respiratory distress and unilateral bloody nasal discharge.
- Clinical signs included inspiratory stridor and failure to respond to antibiotic therapy for presumed pneumonia.
- Endoscopic and radiographic examinations identified a nasopharyngeal mass impinging on the soft palate.
Findings:
- Histopathological analysis revealed a mesenchymal tumor composed of spindle cells with cross-striations, positive for desmin and myoglobin.
- Immunohistochemistry confirmed the tumor as a rhabdomyosarcoma, a rare soft tissue neoplasm.
- This diagnosis was established post-mortem after the tapir succumbed to the condition.
Implications:
- Rhabdomyosarcoma, though common in human nasopharyngeal regions, is infrequently reported in non-domesticated mammals.
- Neoplasia, specifically rhabdomyosarcoma, should be considered in the differential diagnosis for young animals presenting with unilateral nasal discharge and respiratory stridor.
- This case underscores the importance of advanced diagnostics in wildlife medicine to identify rare conditions and inform conservation efforts.
