[A case of pulmonary dirofilariasis diagnosed by biopsy, immunological tests and the clinical course without operation].

A 52-year-old woman who was a pet trimmer by occupation and had four cats, presented with cold-like symptoms. Her chest radiograph and CT scan on admission showed a tumor about 4cm in size with spicula and ground-glass opacity in the right middle lobe. We performed fiberoptic bronchoscopy and CT-guided percutaneous needle lung biopsy on the suspicion of lung cancer, but the tissue consisted largely of granulation tissue with eosinophilic infiltration and no findings of malignancy. The cold-like symptoms subsided and C-reactive protein became within the normal range. Because of the histological findings, her occupation and her pets, we suspected pulmonary dirofilariasis. We asked the National Institute for Infectious Diseases for specific IgG antibody assays to various parasite antigens, which showed positive finding for pulmonary dirofilariasis. We therefore diagnosed pulmonary dirofilariasis and did not perform an operation.