Dirofilariasis of the breast: sonographic appearance.

Human dirofilarial infections characteristically manifest as pulmonary "coin" lesions or as subcutaneous nodules. A case of subcutaneous Dirofilaria infection of the breast involving a 25-year-old woman with a painful breast lump is presented. The patient had not traveled anywhere and did not have any animals, but provided a history of being bitten by mosquitoes. The suspicion of a parasitic infection was raised by the presence of rod-like structures within a hypoechoic nodule on sonography; movement within the nodule was detected during the examination. Histopathological examination revealed viable, adult female Dirofilaria repens, a nematode that is commonly found in dogs, cats, and wild mammals throughout parts of Europe, Africa, and Asia.