Human pulmonary dirofilariasis: uncommon cause of pulmonary coin-lesion.

Pulmonary dirofilariasis is a rare entity caused by Dirofilaria, a dog worm that is transmitted to humans by mosquitoes. The filarial nematode enters the subcutaneous tissue, travels to the right ventricle, dies and then embolizes the pulmonary vessels causing a small pulmonary infarction, which subsequently appears as a solitary nodule. Although these nodules are usually identified incidentally by chest radiography in asymptomatic patients, the lesion is generally presumed to be neoplastic. Diagnosis is made by surgical excision. Awareness of this benign entity is important in the differential diagnosis of pulmonary coin-lesions.