Suspected malignant mesothelial cells in bronchoalveolar lavage fluid of a dog with respiratory distress

An 11-year-old neutered female Labrador Retriever presented with a 1-week history of respiratory distress, lethargy and anorexia. On physical examination, the dog exhibited dyspnea with a rapid and shallow breathing pattern. Thoracic radiography showed diffuse nodular or miliary interstitial patterns, which raised suspicion of bacterial, fungal and parasitic infections and metastatic tumors. Bronchoalveolar lavage (BAL) was performed and the culture yielded no growth of infectious agents, including bacteria and fungi. A presumptive diagnosis of pulmonary mesothelioma was made based on malignant mesothelial cells on BAL fluid cytology. Therefore, this is a report identifying suspected pulmonary mesothelioma using BAL fluid in a dog.