Mediastinal Ectopic Thyroid Carcinoma and Concurrent Multinodular Pulmonary Fibrosis in a Horse.
Authors: Manso-Díaz Gabriel, Jiménez Martínez María de Los Ángeles, García-Fernández Rosa Ana, Herrán Ramón, Santiago Isabel
Journal: Journal of equine veterinary science
Summary
# Editorial Summary Ectopic thyroid carcinoma—a malignant tumour arising from thyroid tissue outside its normal anatomical location—represents an exceptionally rare mediastinal pathology in equine medicine, with this 2019 case report of a 30-year-old Standardbred gelding being the first documented occurrence in the species. The diagnosis was established through a combination of clinical presentation (chronic pleural effusion and progressive respiratory compromise), imaging findings (thoracic ultrasound and radiography demonstrating a large heterogeneous cranial mediastinal mass extending across multiple intercostal spaces alongside a nodular interstitial lung pattern), and post-mortem histopathological confirmation. Notably, the concurrent diagnosis of equine multinodular pulmonary fibrosis (EMPF) adds diagnostic complexity to this case, as the nodular pulmonary infiltrates could easily be attributed solely to the mediastinal mass effect or secondary pleural effusion rather than representing a distinct pathological entity. For equine practitioners, this report underscores the importance of maintaining a broad differential diagnosis when encountering mediastinal masses in older horses presenting with chronic respiratory signs and pleural fluid accumulation, and highlights the need to carefully evaluate pulmonary parenchyma independently, as concurrent pulmonary fibrosis may coexist and require specific consideration in prognostic discussions with owners. Given the advanced age of this patient and the progressive nature of both conditions, early recognition through multimodal imaging remains crucial for appropriate case management and realistic outcome counselling.
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Practical Takeaways
- •Chronic pleural effusion in horses warrants thoracic imaging including ultrasound and radiographs to rule out mediastinal masses, including rare ectopic thyroid carcinomas
- •When nodular interstitial lung patterns are identified, consider EMPF as a differential diagnosis even in the presence of other concurrent thoracic pathology
- •Be aware that ectopic thyroid tumors, while rare, can occur in the mediastinum and should be included in differential diagnoses for cranial mediastinal masses in horses
Key Findings
- •A 30-year-old Standardbred gelding presented with chronic pleural effusion caused by a previously undescribed mediastinal ectopic thyroid carcinoma extending from the 5th to 11th intercostal space
- •Concurrent equine multinodular pulmonary fibrosis (EMPF) was identified as nodular interstitial pattern on thoracic radiographs
- •This case represents the first documented report of mediastinal thyroid carcinoma in horses
- •EMPF should be included in differential diagnoses for nodular interstitial pulmonary patterns, particularly when concurrent mediastinal or other masses are present