Pulmonary dirofilariasis: a diagnostic challenge.

The canine heart worm, Dirofilaria immitis, can occasionally cause pulmonary granulomas in man. Fewer than 100 such cases have been reported in the United States, mostly from along the Atlantic Seaboard and Gulf Coast. None of these cases have been from the Mississippi Valley states. We have described a patient with a 14-year history of smoking, a patient in whom an enlarging pulmonary nodule was found. The resected nodule contained a filarial worm. This case illustrates the difficulty in distinguishing these lesions from neoplasms.