Pulmonary dirofilariasis mimicking malignant pulmonary lesions: Two cases presenting as solitary and multiple pulmonary nodules

Pulmonary dirofilariasis is a relatively rare zoonotic infection caused by Dirofilaria immitis, which often presents as pulmonary nodules mimicking primary lung cancer or metastatic disease on imaging. Herein, we report two cases of pulmonary dirofilariasis diagnosed using video-assisted thoracoscopic wedge resection. A man in his 60s with an 8-mm solitary pulmonary nodule and a woman in her 70s with multiple pulmonary nodules detected during follow-up after endoscopic submucosal dissection for intramucosal colorectal cancer underwent thoracoscopic wedge resection because malignancy could not be excluded. 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) demonstrated only mild or absent fluorodeoxyglucose uptake in the lesions. Histopathological examination revealed cross sections of D. immitis within the pulmonary arteries, confirming the diagnosis of pulmonary dirofilariasis in both cases. As pulmonary dirofilariasis closely resembles malignant pulmonary lesions on imaging, preoperative diagnosis remains difficult. Accordingly, this disease should be included in the differential diagnosis of solitary and multiple pulmonary nodules. Video-assisted thoracoscopic wedge resection provides a valuable approach as it provides definitive diagnosis and curative treatment.