Pulmonary dirofilariasis: the great imitator of primary or metastatic lung tumor. A clinicopathologic analysis of seven cases and a review of the literature.

The clinical, radiologic, and pathologic features of seven patients with pulmonary dirofilariasis were studied. The findings were analyzed in conjunction with those of 76 cases previously reported from the United States. We found that, in most instances, the disease was acquired in states along the Atlantic and Gulf coasts and occurred predominantly in whites (94.7%) in their fifth or sixth decades of life, with a male to female ratio of 2:1. Symptoms, commonly chest pain, cough, or hemoptysis, were present in 37.6% of patients. Most patients (62.4%) were asymptomatic, and the disease was discovered incidentally on routine radiography or during the investigation of another problem. Peripheral eosinophilia was present in 20% of patients. The radiologic findings consisted of single (89.8%) or multiple (10.2%) pulmonary nodules that simulated primary or metastatic lung tumor. Dirofilariasis was not included in the clinical differential diagnosis in any of the patients. In one case, the diagnosis was accurately obtained by fine needle aspiration biopsy. All other patients required thoracotomy with excisional lung biopsy for diagnosis. Pathologically, the dirofilaria nodule consisted of a spherical subpleural infarct with a central thrombosed artery containing Dirofilaria immitis in various stages of disintegration.