Granular cell tumor as a cause of chronic cough

A 6-year-old warmblood mare was presented at the equine clinic of the University in Giessen due to a suspected recurrent airway obstruction. Subsequently, the mare developed increased coughing despite low dust exposure and anti-inflammatory treatment with glucocorticoids. A bronchoscopy revealed a mass in the right main bronchus. On radiographs of the thorax multiple, focal soft tissue dense opacities over the entire lung field were visible. At necropsy multiple well-defined white soft-elastic masses up to 40 mm were detected in the right lung. On histology these masses were either located in the peribronchial tissue or expanded occasionally into the bronchial lumen. Neoplastic cells were seen in the masses but also in the sinusoids of the pulmonary lymph nodes. These neoplastic cells had numerous granules in the cytoplasm. Luxol-Fast-Blue stained these cytoplasmic granules deep blue. The PAS reaction of the granules was variable and the immunohistochemically detection of S100 antigen and vimentin were positive, while GFAP was not detected. Finally a diagnosis of a Granular cell tumor was made. To the knowledge of the authors, this is the first report on a granular cell tumor that was associated with tumor cell emboli in the regional lymph nodes.