Four cases of pulmonary nodular eosinophilic granulomatosis in dogs

Four cases of pulmonary nodular eosinophilic granulomatosis are described in dogs. All dogs were presented for chronic respiratory disease. Three dogs had radiographic and pathologic evidence of heartworm disease. One dog had lesions suggestive of past heartworm disease; but adult worms were not found at necropsy. Radiographically, single or multiple pulmonary densities up to 10 cm in diameter were seen. Hemograms on 3 dogs indicated a leukocytosis, neutrophilia, and eosinophilia. A microfilaremia was not detected in any of these dogs. Transtracheal washes yielded eosinophils, neutrophils, and macrophages. Three dogs were euthanatized. A 7 cm pulmonary nodule was excised surgically from the other dog. The pulmonary nodules were grossly yellow to gray in color, well-circumscribed, and solid. In one case, several nodules surrounded major branches of the pulmonary artery. Histologically, these nodules were composed of dense accumulations of epithelioid cells, macrophages, and eosinophils. There was no evidence of thrombosis due to Dirofilaria immitis. Possible pathogenetic mechanisms are discussed. Differentiation of pulmonary nodular eosinophilic granulomatosis from other types of pulmonary nodules in the dog can be accomplished by histologic examination.