Granular cell tumours in the lungs of three horses.

This research article explores the occurrence of granular cell tumors within the lungs of three horses. These tumors, also known as myoblastoma or putative Schwann cell tumor, are rare but considered the most frequently cited primary lung tumor in horses.

Study Overview

• The study describes the clinical findings of three adult horses presenting with granular cell tumors. Diagnoses were made at the Veterinary Medical Teaching Hospital, School of Veterinary Medicine, University of California, Davis.
• All horses were bright, alert, and without fever at the time of presentation. They exhibited several abnormal clinical signs such as increased pulse or elevated respiratory rates, thin body condition, cough, nasal discharge, nostril flare at rest, apparent abdominal effort during expiration, and decreased or absent breath sounds over one hemithorax.
• The research involved a thorough investigation into the horses’ health, including routine hematological and biochemical analysis.

Findings

• Each horse presented unique health abnormalities. Horse 1 showed leucocytosis, mature neutrophilia, lymphopenia, hyperproteinaemia, and hyperglobulinaemia. Horse 2 displayed hyperproteinaemia, hyperfibrinogenaemia, and hyperglobulinaemia with a normal leucocyte count. Horse 3 presented no abnormalities.
• Ultrasonography revealed diminished movement of the pleural surface in horse 1’s right thorax and horse 2’s left thorax. Radiographs suggested diffuse nodular masses in two of the horses and an expansive area of increased pulmonary opacity in one.
• Bronchoscopic examination disclosed nodular masses jutting out from the right main stem bronchus in two horses.

Conclusion and Actions

• Pinch mucosal biopsies of the masses led to the diagnosis of a severe, chronic, neutrophilic, hyperplastic tracheitis with intralesional cocci in horse 1. In horse 3, the tissue samples were too minuscule for interpretation.
• Despite the non-diagnostic biopsy, a primary pulmonary tumor was suspected in horse 1 because of increased respiratory distress, leading to euthanization. Similarly, horse 2 was also euthanized due to suspected pulmonary abscess or neoplasia but without performing further diagnostic procedures.